Need help understanding VLANs and whether I need them

[EngChi]

Looking to update/revamp my home network with goals of isolation/increased security. Also would like to figure out if I can solve dependency on domain controller (when I reboot W2012 server PC internet access stops)

Have 3 'groups' of devices
1. Windows domain consisting of W2012E server plus 4 computers (game PC, work PC, 2 laptops). I want for this to see each other, be able to print to networked printer, and see media on the NAS, have access to internet

2. Media set - Synology NAS, 2 media players (Shield +Amazon Fire TV), Denon AVR, Linux workstation hosting Plex, networked media tuner (HDHR). I want for these to see each other, and have access to internet. I don't want for these to connect to Windows domain or be able to communicate with it

3. Internet access only devices (obihai adapters ,etc). I don't want to these to see anything internally.

Not sure whether all mobile devices are in group 2 or 3 yet.

So, are VLANs an answer to what I want to do? I am trying to read up on what I should expect domain controller to do vs some other device.

Current config
ISP -> Mikrotik Hex 3 (router) -> dumb switch

Intended config
ISP -> hex 3 (or Unifi security gateway if I understood its purpose correctly) -> Unifi Switch (for wired) + Unifi AC (for wireless).

thank you!