Is it safe to remove my old AMD folder?

On my C-partition and D-partition I have a folder named TestDel[driveletter]; I move certain folders like the one you described into the appropriate TestDel folder, such stays there for a month or two, sometimes longer. If after a couple of OS and data partition backups later, Windows does just fine without said folder, then I finally delete said folder from within TestDel[driveletter].

If the folder is in the main C: folder, then you should be all right to delete it. It just contains install files that the installer never seems to clean up. Grrrr,

Since you went Nvidia, you should be able to remove the AMD folders under \Program Files and \Program Files (x86).

I would first use Window's uninstall feature to remove the AMD graphics drivers if you haven't already. Under no circumstances remove the AHCI or USB drivers. Do the custom uninstall to make sure that you don't remove these drivers. You won't be able to use a USB keyboard/mouse if you do, and it's really tough getting them back in with a PS2 keyboard (if you have one) and no mouse.

Just remove the AMD video card driver and software.

there's a software available for that. you may want to use "display driver uninstaller"

No. Just uninstalling through Control Panel and deleting the folder afterward will be fine.