Confused as hell on modern geometry fit
So I'm looking to replace my 10+ yo light trail FS bike , and am utterly baffled by the correct fit for a modern steep ST , slack head angle bike. This is for a do it all bike, mostly tighter mid Atlantic undulating trails, rather than long up followed by long downs. Like to go fast when I can but old now and not rad at all on a bike can't afford to break upper extremities due to work ,so allergic to big air.
Specifically I was looking at the Ripley AF, but nobody locally has any in stock to check out. Looking at Ripleys sizing, at almost 6'1 (185cm ) I'm exactly between a L an XL. Consensus on forums FWIW tends to get the bike runs small so go XL, but one local shop things trying to fit a L is better due to the local trails needing more low speed maneuverability. Confusing things even more, looking at stuff like RAD distance calculators , unless I'm doing it wrong, it looks like that considers a L frame even on the long side with it's 475 reach .
I get that RAD distance and reach / stack involve standing measurements, but what about prolonged seated pedaling which is what we do a lot around here? Im guessing with the steep seat tube angle, the ETT length here is fairly short even with a long reach. How the hell do I know if the L is big enough with this type of geometry for this type of riding?