No need to reinstall windows.
Any impact in gaming will come from the graphics hardware change.
Hopefully, you made a significant jump in graphics capability, or you may be disappointed.
Windows is quite happy to run several different graphics drivers, so you really do not need to remove the amd drivers, but you could.
Some will suggest you also run a driver cleaner program; I don't know that cleaning is necessary either.
You might just take a system checkpoint before you do anything. Then if something goes awry, you can restore to where you were before you started.