I can't say that there's much difference between setting up a Shimano mech and an XC Pro. Both have a "hi" and "lo" screw, a b-screw and a barrel adjuster.
If you can set up a Shimano mech, you can set up a Suntour as well. It's no black magic.
If the XT one works that good straight away, you either have a bad Suntour mech or a problem with the jockey wheels or something.
Quoted for emphasis.
And to drop an additional bit of info; afaik the SunTour Shifters for the rear derailleur have no "7-speed - 8-speed" switchable option, only a marking "f - index" (letters Index
not printed). 7speed SunTour cassettes can be controled by 8speed shifters with no fiddling.
_________________Specialized RockHopper 1988 rebuild thread
Cannondale SM 2000 (1991)
, Specialized HardRock Cruz (1991), Specialized RockHopper Comp(1988)