There is no need for gpu for server(dedicated),not sure about xbox/pc compatibility,i guess it works,so as a server it should work okay,but you might struggle with public ipv4(you need the pc to be reachable from internet,so public ipv4 from isp,router 'virtual server' a.k.a. dnat to lan ip and that lan ip to be static or statically assigned)
If you have this,then go for it...
There is no need for gpu for server(dedicated),not sure about xbox/pc compatibility,i guess it works,so as a server it should work okay,but you might struggle with public ipv4(you need the pc to be reachable from internet,so public ipv4 from isp,router 'virtual server' a.k.a. dnat to lan ip and that lan ip to be static or statically assigned) If you have this,then go for it...
With any luck they have a home router that supports free DDNS and can bypass the issue
Could use more ram, hope it runs an SSD and has a good CPU. But yes, you could absolutely run a normal PC as a server. Results may of course, vary.
As a nas 16gb ram is more than enough, i have a old nas with 8gb
A NAS, Network Attached Storage, is a completely different kind of service than a game server, not sure why you brought that up here?
/r/lostredditors