Short and sweet... what make/model/brand 210 cabs go great with my GK RB700II? Lightweight is a big plus. Not on a budget. Deep, fat, punchy, tight are all key words. Mainly playing fretless.
Seems like the GK neo 210 might be an obvious suggestion. I've found that the SWR Golight 210 is loud light and low and it works pretty well with that grindy GK tone too.
Have a go and just try a bunch of cabs, you won't have a hard time finding a lightweight 210 that sounds great with that amp. Good luck!