Question 1: do i need to unplug all GPUs while installing drivers, then only plug them back in after driver install is complete?
Its best to start with 1, and then plug them in 1 by one if you're unsure of the cards being good. If they're all new its fine to just plug them all in.
Question 2: do i still need to run pixel-patcher with more current versions of AMD drivers? I was always using this when using v17 & v18 drivers but wondering if this is still required with their v19 & v20 drivers.
Yes, you still need to. Also dont use the ver 20 drivers, stick to 19 or older.
Btw since you are using windows, you wont be able to mine eth with 4 gb cards, you would need to switch to something like simpleminingOS.