I would pay more attention to the Top Tube length than anything, as a short one makes for a cramped ride and a really long one may be too stretchy. Someone 6 ft 3in with a 34" leg I reckon would want an old-school 23" field gate style MTB for general utility/ leisure riding, or maybe a 21" of they want a bit more standover clearance to protect one's delicate bits if riding on rough stuff!
Here's two Raleighs, both 1991 bikes with 501 frames. the black one is 23" the multicolour one is 21", both have the same reach, frame geometry, same head tube height. At just under 6ft with a 33 1/2" leg, I can ride both fine, but the black one has to be treated with more respect:-
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