Server next - Gaming PC build almost complete

So I have just about finished my gaming PC, save on cost I took AM4 route, using a Gigabyte X570s UD with Ryzen 9 5900X 64GB RAM, just waiting on GPU which so far I am leading to the 4070 ti super for gaming with ray tracing but also so far better option for 3D animation and modeling with my 3D printer…
The case I have is a Phantek Enthoo Pro 2 which has space for a mini-itx board, so thinking of using that space to place my sever, as I also have in hand a Phantek Revolt x 1000w PSU so I can power 2 systems independently … so after looking around finding it hard to find a mini-itx suitable and with enough storage to go along. Be used as a cloud storage, VM for various testing such as smart home, program learning with my daughter for her home education. Home NAS storage for our family videos photos, and to rip our DVD and BluRay collection to, to run either PLEX or the other app (name I have forgotten)… will also run off a backup to the cloud specifically the family photos videos and important docs - this way I have a back up from our main at home, and then the cloud- also before I forget regards to VMs the idea to learn in this field to, as I am in process of learning AWS, so will have VMs which again as part of my daughters home education to learn as well, from AI, Data analyst, programing as mentioned, but also setting up small weather monitor project using a PI with sensors etc, so the VM would collect the data and store historically to mess around with, one of several projects she wants, as shes talked about programing for a small robot that can follow her lol- but something like Proxmox for the VM etc… and add more VMs as I go
the budget is under £300, cheaper the better have capability to add a GPU (messing around with the idea of minecraft server as well a gaming server) but the GPU is not in this budget looking at RX 7900 xtx for this, its just to get the server
up and running -

It seems like a less than ideal plan to put the server into the same chassis and on the same psu as a gaming pc.
You’re asking to run a TON of stuff on an itx board which is generally not compatible with a low budget number.
Definitely recommend, at the least, having the server separate. And not itx based.