Firstly, don’t think I am loaded here this is an ideal list that I will chip away at over time - https://pcpartpicker.com/list/xVL9kf
I am looking at getting a fractal desigm north xl second hand, I presume there is no danger in that other than standard non new concerns.
Are case models universal or will I need a specific motherboard and then specific cpu/gpu etc.?
https://pcpartpicker.com/list/tYpnPJ
PSU
Did some checking and my favourite shop recommends 800W PSU for the 7900 XTX 24 GB GPU so I switched yours out for a Seasonic 1000W - https://hwbusters.com/psus/seasonic-focus-gx-1000-atx-3-2024-psu-review/
Seems to be other PSUs with better score according to my link, feel free to read and switch.
Gives you lots of power available if you wanna add a bunch of hard drives to it later on when your Jellyfin library grows.
RAM
I changed your RAM to one that is listed as supported at https://www.msi.com/Motherboard/MAG-B850-TOMAHAWK-MAX-WIFI/support#mem
CPU Cooler
I found out Thermalright has released a better CPU cooler this year so I added that one to your build.
This is the Noctua I mentioned, but I believe the Thermalright I added is very close to Noctuas best air cooler at half the price.
https://pcpartpicker.com/product/8c88TW/noctua-nh-d15-g2-9158-cfm-cpu-cooler-nh-d15-g2
Storage
I also downgraded your M.2 speed to PCIe Gen4 but made it a single one and larger. To avoid any mess between PCIe slots and M.2 slots I recommend using the PCI_E1 slot and M.2_4 slot
https://www.msi.com/Motherboard/MAG-B850-TOMAHAWK-MAX-WIFI/Specification