Experience is your best friend. 7 x 50's can be held well. and are the best entry level bino's for you.
The problem you have eluded to is very real for the bigger sizes. The tripod is a unsatisfactory platform. 20 x 80 or 100 are very good bino's, but are almost useless if not able to be held firm. The central clamp is only as good as its weakest link.
I have used a wooden framed parallelogram which was well balanced and stable. The size and wight of such equipment prohibits portability.
Elbows on a fence post works better for most of us.
You need to try before you buy... That is the only advise you need.