What software would you even use for such a vm, I'm not too familiar with linux software
I'm an ubuntu user myself
and wouldn't it run quite a bit slower than native windows anyway?

Also, if you have multiple GPUs you can use one just for the VM and one for running Ubuntu

I don't have two GPUs but I do have two SSDs of similar speed. Would it somehow be possible to dual boot and use the second one as a VM at the same time? That would be a lovely solution for me.

(So I can boot into windows if i need it for a specific application where the VM isnt optimal, and otherwise i just use ubuntu with the vm to run my applications - or just run ubuntu without the VM even)

In order to fully accomplish making a VM inside Ubuntu, I reccomend using something called "QEMU", which is the VM hypervisor itself. QEMU essentially does all the hard work, for a VM manager (something to look at your VMs with) I recommend Virtual Machine Manager (VMN)

If you want a in-depth guide on how to create a single-GPU accelerated setup, I reccomend this guide (for Ubuntu):

https://github.com/Andrew-Willms/GPU-Passthrough-On-Ubuntu-22.04.2-for-Beginners