How to handle stealth & detection without bogging it down?

I have so much to say about stealth in the game, but I won't bore you with most of it. Stealth, though, is the system that highlights to me most directly just what Pathfinder 2e is as a system, and how it's not what many of the game's most vocal online fans seem to think. In short, the Stealth system highlights that PF2e is much more simulationist and fiction-focused than most people are willing to admit (which is not to say that it is a simulationist game, just that it is making some pretty direct but oft-overlooked efforts to be as flexible and multi-purpose as possible).

Party stealth is a multi-comparison system in no small part because hiding and perceiving things in real life is a multi-comparison system. In real life, it's just not systematized. But also in real life, you only need one person on your team to be detected by one person on the other team for the other team to mobilize. This hints at multiple ways to track the interactions, or multiple ways to modify Stealth to help create a smoother experience.

Unfortunately, I don't think any method really works well, like, in Pathbuilder. But Pathbuilder's GM mode should make it easier to see what the actual Stealth rolls are.

The first thing that I do when preparing a pre-made encounter, or crafting an encounter in advance, is create a table and pre-roll initiative for the NPCs. I'll usually do this on my laptop, in Excel or in my note-taking program. Rolling initiative first isn't actually important here, especially if you're using something like Excel which will let you easily re-order the table, but it helps create just one table if you're doing it on paper. The table includes the initiative roll, some signifier of the skill used for initiative, and the NPCs key stats: Perception, Ref, Fort, Will, AC, and max HP, (plus columns for current HP and status). This helps make stealth roll comparisons much easier.

You then compare the max Perception DC to the lowest Stealth roll. If Stealth wins, everyone is Undetected (or Unnoticed, if you're at my table, because screw that discrepancy). If not, I'll jot down which PCs the NPC notices. After this, I'll switch to initiative order for comparisons. I'll make note of the first NPC's Perception DC and then compare it to all of the Stealth rolls to see who's noticed, and make note. If it's everybody, I stop there. The first NPC will spend their turn pointing out the hidden PCs to everybody else. If there's anybody left after that, I move down to the next NPC and only check the remaining PCs.

This can be streamlined, but doing so involves allowing for contested skill checks. Instead of comparing the Perception DCs to the Stealth rolls, you can instead choose to compare the NPCs' Perception-based initiative rolls to the PCs' Stealth-based initiative rolls. Following the procedure above, this actually cuts out one of the steps.

Multiple comparisons can also be reduced if you just let the lowest roll stand for the whole party. Then you're just comparing the lowest stealth roll to the initiative rolls.

To overcome the writing space issue, pick up a clip board. It's back-to-school season in the northern hemisphere, you should be able to find something on sale right now without any problems.

For actually tracking the changing stealth statuses during play, how you play is important information here. You say the table is small -- does this mean you're not using maps/minis? If you are, you should actually be able to tell at a glance for most creatures whether someone his hidden or not at the time the player rolls Stealth to hide. The actual range of Perception DCs should be small, and with them written on a clipboard or spreadsheet, you can hopefully just make a mental note and remember. If you have a lot of NPCs, that might be harder to do, but with 2 - 6, it should hopefully be OK with a little bit of practice.

Concealed/Undetected is slightly more complicated, but it makes a lot of sense in the context of the fiction of the game, and I've found that that makes it a lot easier to track. Standing behind something that crates partial blockages to line-of-sight (such as a bush?) The enemy can't quite tell where the edges of your body are! Concealed! Hide and successfully snuck away without anyone noticing? Undetected! Wearing camouflage but standing in the open? You have fuzzy visual boundaries! Concealed! Standing in a thick fog cloud? Fuzzy boundaries again! Concealed! Ducked around a corner, out of line-of-site and then moved in a way that no one could reasonably hear you (i.e. used 'Sneak')? Undetected! Ducked around a corner, out of line-of-site, but didn't sneak away? Hidden! Ducked around the corner, but ran away so that the NPC could hear your movements? Hidden!

If you want, you can assume the state applies to every NPC on the board until you look down and see where that doesn't make any sense. Or, you can make it apply to every NPC on the board, but extend Seek to allow NPCs ot make an unlimited range, 360 degree Perception check for stealted creatures that they have line-of-site on (this super-charges Seek, and kind of nerfs stealth, but making it cost an action turns it into an active choice with an opportunity cost). You could reduce it to 180 degrees for the sake of better empowering stealth (and also introducing better sense of directionality to sight).

It sounds like you might be using the Pathbuilder Encounters tracker? It puts everyone's perception bonus in a fairly prominent spot without needing to actually click on each creature. You'll need to mentally add 10 though. In most combats I run, there are usually only 3 or 4 different creatures at most, so even if the total number of enemies is higher, the number of DCs you need to compare to is comparatively low.

I'm a big proponent of offloading mental effort from the GM to the players whenever possible, so I would rely on players to keep track of their own detection levels for the most part. Unless there's a big reason you want to keep it secret, just let them know who they successfully hid from and who they didn't. Or have them keep track of their current stealth score and ask them for that number when it's the turn of a monster that might want to attack them. They should usually be playing between Observed, Hidden, and Undetected, and they'll probably know which one of Hidden & Undetected they're in (presuming they're in at least one of them) based on when they've moved, so usually a player should be able to handle that bookkeeping.

My experience is that it's rare that more than one or maybe two characters will want to do stealth during combat. Outside of combat it's more common, but that's not so relevant here. This keeps the amount of mental overhead necessary pretty low.

I tend to be pretty loosey-goosey in combats though. If I've got 8 enemies of 3 different types, I'll usually try and roughly remember which one went first, second, third, etc. and apply the damage based on that. But I don't actually write down anywhere "Wolf 1" that can actually easily track between Pathbuilder Encounters and my physical battle map, and I don't doubt that I make errors in whose turn it is or which enemy is receiving damage all the time. I just let it go. The same total number of turns are happening each round and the enemies have the same total HP, so I figure it mostly balances out. My approach above works for running stealth in that context, but if you're really concerned about it all being precise, it might not work quite as well for you.

P.S.: Go Enlightened!