My person preference, for me, and only for me is an 8'6"....for the type of fishing and locations you mention.
I find I am more accurate with an 8' 6", and it seems to load better, for me, at shorter ranges. When I am in a boat however, for me, the 9' kind of comes into it's own. On shore, walk and wade stuff, the 8'6" works better.
You need to cast both lengths before deciding for yourself. When you test cast, make sure you aim at some targets, at 2 ranges, suggest 30' and maybe 45'.
Also suggest you just use your 6 wt for now and decide later once you get some time on it. Suggest lawn casting at targets as well, which you can do right today if you wanted.