Draining the cooling system is so quick I would just do it. Getting the radiator out of the way involves, what, two 10mm bolts? Just do it, it's quick. I also removed that inlet on the top and replaced the oring. It was old and cracked/leaky. You're right anyway, I doubt you'll have to pull cams to adjust. Mine needed some tweaking, but... an easy life this engine has not had.
As far as the carbs go, just get in there and own it. It's a carb'd bike and you know carbs like to be understood
Time to get in there and learn the vacuum mess.