Any Xinput controller (360, DS3/DS4 with SCP, etc.) should work, but the control scheme was never update to work the same as the 360 version, which is disappointing.
For mods all you really need is FCR2. It changes so much that a ton of other mods aren't compatible with it anyway. I think one of the zero weight mods on the Nexus is compatible with it though, and that's pretty nice to have because that shit gets old fast. There's also a mod that removes the extremely annoying visual effects from dark equipment, if you play on dark difficulty. I can't remember if it's easy to get to work with FCR2 though.
Oh, and you might want to grab a Witcher 1 endgame save if you don't have one.