Good start to your exploits, good luck.
Regarding pellets I have a, now old, Titan Manitou (pcp) tried Bisley magnuns as rec. by Falcon who say they set their guns with these 'heavy' pellets. They do drop off quite a bit with 12ft lb.
I have found that a pellet weighing around the 16 grain mark is ideal, try Air Arms field the Titan loves them.
At the end of the day it is as has been said, trial and error, find the right pellet for your gun and stick with it.
I seem to remember one company offering a trial pack of pellets poss about 20 of various types but cant remember who!