BTW your “server rack” is really a network rack, you’ll find that it’ll only hold a small selection of rack mount servers like the Dell R210/20, it’ll be fine if you’re planning on using mini PCs etc
I used to run windows 7 pro (really you need a pro version to get RDP) it was 100% rock solid, did everything it needed to do, was very easy to setup and maintain. If doing this you should obviously use a newer version but forced updates will be your enemy, so google how to disable them but yes for most using a non server OS is fine. However this sub is about home labs, which is meant for learning enterprise software, you’re best posting over in r/homeserver or somewhere else I expect
If you are looking for a proper solution then checkout AC infinity, that'll give you everything you need I expect.
Otherwise you're looking at a self build option of a fan controller and an appropriate power supply, I just used some relatively quiet highish airflow fans in my rack run at a pretty consistent speed using a basic fan controller I 3D printed a bracket for, I might turn them up a bit in the summer if the temps are showing high..
r/homelab is not the sub to gain basic PC or research skills, if you don’t have them then and the ability to do basic googling then you shouldn’t be posting here. This is not r/techsupport