I have a USB HDD that I'm hoping to install Windows on for a few games and other pieces of software. I know my load times will be miserable, but how poorly will things run once on ram? Lastly, Windows does like to screw with other operating systems on the same drive, will it play nice with my main drive as long as it's on the HDD?
Yep, seen this happen a couple of times with friends. Their boot loaders just randomly get nuked from their EFI partition after a Windows update,
You can pass through a single GPU, it's just kind of a pain to get working so I wouldn't really recommend you bother with it unless you really want to go this route. Another option is to pick up some ancient very cheap graphics card up off Ebay or something to use for the host machine then pass through your more powerful GPU to the guest machine.
This is a laptop so could I use the igpu for the host that already runs the UI and pass the GPU through to the VM?
Looking it up supposedly theoretically possible but I think the CPU has to support it https://www.reddit.com/r/VFIO/comments/xpjihb/guide_gpu_passthrough_for_laptops_in_fedora/
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In the US check Facebook Marketplace (or your local equivalent). You can find all sorts of junk on there for less than $20.
Thats where I get half of my garbage from.