it's really heavy topic
1. Unifi controller has written User manual also for unskilled users. Then my recommendation is open it and follow all steps for proper setup + write there your comments (for a better understanding in future). It will be also a training, how to use the controller.
2. Network:
- "Corporate network" for your main LAN (computer, NAS), use also VLAN setting for it
- "Guest" for Guest WiFi portal, you can define there VLAN field, for next "shielding" of such network, e.g. just for connection of your guest to internet, but not for your Corporate Network.
3. Firewall is your best fiend. You have to define WAN IN/OU/Local, LAN IN/OUT/Local, Guest IN/OUT/Local rules
4. Port forwarding also
5. Geo IP filtering or THREAT MANAGEMENT:
a) when you enable Geo Filtering feature, you have to also enable Hardware offload, then you can't use THREAT MANAGEMENT. In Geo IP Filtering you can define lot of possible features. For me it's better to use Threat Management (IDS) when you have WAN download line >250Mb (I have 1Gbps). But try it and test the performance of the filtering.
b) Hardware offload you can setup by the mentioned Unifi controller guide.
c) THREAT MANAGEMENT (better IPS) and its CATEGORIES - you can play with all the categories, even till a time when you chose "Game categories ON" and your children will ask you - why I can't connect to Minecraft?

this is really up to your testing. I will send you a screenshot by PM.
View attachment 1934
6. Definitely you have to enable DPI - Deep packet inspection
Then you will see what happens in your network - STATISTIC section.
You can setup all possible data category visualization (e.g. what IP or named client eat what bandwidth by what category e.g. YouTube streaming, or by Netflix, ...). or you can see all details by client (split of packet inspections).
View attachment 1933
7. for direct Unifi VPNs - Services/Radius
.... we can spend time till next morning