Can I still use Repetier-Host to control the MK4?
I have a MK3S+ and prefer to control it over usb/com, using Repetier-Host.
I find being able to interactively control the printer valuable, (ie connect, move axis, print, see print progress in detail, kill/pause prints if problems occur, move axis interactively, re-print, all from one place.)
I only have one printer, I don't mind needing the PC in the chain, have never suffered from connectivity or power issues, and I don't have a desire for remote operation.
Can I still connect to the MK4 in same way?
RE: Can I still use Repetier-Host to control the MK4?
This isn't exactly an answer to your question, but if you want PC->usb->printer, you can also run Octoprint on a Windows PC ( https://all3dp.com/2/octoprint-windows-tutorial/). This is what I do. So if Octoprint works with the MK4, it might be another option for you.
RE: Can I still use Repetier-Host to control the MK4?
If you go windows path then there is a easier way: https://github.com/jneilliii/OctoPrint-WindowsInstaller
Anyway I expect Repetier-Host to work with MK4 since it just sends g-codes which didn't change (for typical stuff).