Yes, I’d agree with what has been said by Mike & CP re: shoulder width etc. Unfortunately for the wallet, I think bar width/stem length is a case of trial & error…..or just get some open ended lock on grips and slide them inboard on wide bars until you find your preferred width.
FWIW, I have a SC Blur TR and Tallboy LT and am at the upper end of the height range for large – so can appreciate what you’re saying about short top tube lengths. I’ve experimented a lot with stems varying from 70,60, 50 down to 35mm and bars from 720mm to 800mm. I’m a fairly slim build and have found that a 70mm zero rise stem and 750mm width bars offer the best combination of handling and comfort for me. Apart from some specific fast downhill sections of trail, I haven’t been able to really get along with 780-800mm width bars, as I felt that they compromised front end grip on more flowy trail centre type trails.
I recently bought a cheapish Specialized bike that has a longer top tube and low slack geometry, and the first thing I did was whack some 785mm bars and a 50mm stem (‘cos I’m a sucker for fads & fashion!!) but after a few rides, I wasn’t really feeling much front tyre bite and felt a bit too far back when stood on the pedals – so have dropped a 60mm stem on and shoved the lock on grips in to 750mm – and hey presto, more front end grip, comfortable shoulders and still able to get back for very steep tech descents.