What services are worth running on a synology NAS?

Setting up a SDN Controller for TP-Link Omada worked ...then I started down the Proxmox road with different hardware.

Depends on both the model and your expectations.

Some models support hardware transcoding so Plex/alternatives work just fine on them.

If you have a model with a couple GBs of RAM then the world is pretty open with Docker containers.

The CPUs are fairly slow though so game server hosting and anything high speed is a no go. I mean, it’ll “work” but you probably will be wanting for more.

DS File is very handy.

Docker hosting valtwarden is very nice too

None, stop trying to hyper-converge everything. Synology makes nice storage boxes and their apps for backup are solid too. Leave it at that.