well I have done both
most of my main tree stands now have shooting rails I use as a rest, , some came with them, some I had to make out of PVC pipe, I also use the rails as a way to place camo all around me too, to help me blend in best I can, and help hide movements
cross bow are big and bulky if you ask me
and in a ground blind I tend to you my knee's, but have used a tri pod too, but not a major need to me for one
other wise I am free handing shots( haven't had to free hand a shot in a few yrs however)
but if I have a way to use a rest of any sort, I am, or kneeling if possible too
free hand shooting leads to misses more than with a rest, so I prefer to take all the help I can get when its time to shoot
as for sighting in, I sight in off sand bogs just like I do with my rifles, off a bench, rock solid that way