Not exactly like DisplayFusion, but virtual desktops have been a thing forever on Linux. There's a ton of options in that department. They don't work the same in each DE, so if it doesn't work in yours try another. I believe COSMIC supports this already, otherwise in the tiling department you might like Sway or Hyprland. KDE and Gnome are a bit weird with per-monitor virtual desktops, and KDE at least is working on it.

USB Passthrough: yes, either the device node itself or the entire controller via PCIe passthrough.

Premiere, I believe so but you will need GPU passthrough for that to work to any degree of smooth. GPU passthrough is super nice when it's all set up, worth the spend for a second GPU. Performance is near identical to native, it's really great. Been gaming in a VM for years... out of convenience.

I don't know if I correctly understood but I think that KDE plasma has this functions you need from DisplayFusion. You need to use Virtual Desktops + Activities, both inhetit to KDE

Maybe I didnt undertand correctly, but I think this may do the job for you

Not exactly what you're asking for but you should look into tiling window managers, if I'm understanding correctly they do almost exactly what you want

For example on my laptop if I open Firefox it opens in full screen, if I open a terminal it resizes Firefox to half the screen and opens the terminal in the other half, a third and it splits whichever window I'm focused on vertically etc etc

You could achieve what you want by having the VMs in windowed mode and just using a tiling wm

You get the added bonus of virtual desktops that you can flick through with mouse buttons/keybinds/3 finger swipe if you want multiple layouts of different windows

Also I've not used it but I'm pretty sure hyprland has something called fake full screen where it tricks windows into thinking they're full screen while actually being windowed

Most of the "software that runs only on Windows" runs perfectly on Linux with wine, including the installation software, and the integration into the app launcher on all of the Linux distribution that I know.

For a widow manager, I don't use one, i have many virtual desktop and as it's smoother than in Windows, I use only that (i don't remember how virtual desktop works on ubuntu)

Première run really badly in VM, and run it with wine is highly messy, do to poorly designed Windows install soft and plenty of missing dependencies, there are linux alternatives that do nearly the same job : KDEnLive, Shotcut and Openshot.

That all I can tell for now, I hope it will help you a bit. Ps: try other linux distribution before doing an installation to find the desktop manager that you prefer.

i think you can do this with xrandr. it usually works on "outputs" but i believe you can define virtual monitors as well.

also, you'd do well to look into tiling window managers like i3 or hyprland. that may be closer to what you actually want.