you can create them afterwards and move the stuff into the subvol. do it from a live usb and don’t forget to update fstab. be sure to use rsync with the flag to keep permissions etc
i have 2 screens, i use a grid of 20 desktops for each screen. the grids are synced between the screens, if i go left on one screen, it goes left on the other
i have tiling; i use bismuth to add the tiling to kwin. i have set up shortcuts like meta+f makes a window float etc
i have an mx master mouse with the thumb button and other configurable buttons. i have logiops to remap those. clicking the thumb button will bring up the desktop grid. thumb+up goes a desktop up, etc… this is extremely comfortable to use
i have configured the task manager in the panel to only show apps opened in the current virtual desktop. this way i can have a Firefox for each row for example.