What should I look for when buying a new road group set?
You need a rim brake group set with a comparable brake reach as before, which will happen automatically if the new one is also Campy because convetional Campy calipers have only come in one reach in the past decades.

If the new group is Campy then you can use a 12 or 11 speed cassette on your existing wheel without issue. If you switch to Shimano or SRAM you need a different freehub body, which may or may not be available to retrofit your existing wheel. Most third party Campy-compatible hubs that receive such long term parts support at all do have these available. The idea is also out there that 11 and 12 speed cog spacing respectively are close enough between SRAM/Shimano and Campy that it doesn't matter. I'm personally down on the idea of setting up a high-end bike like that and expecting optimal performance, but it does function.

All groupsets have ISO bottom bracket shell compatible cranks of one spindle type or another available, but some (SRAM) also have BB30/PF30 ones that won't fit your shell, so you'd need to choose the compatible BB/crank option in some cases.