Yes, The first the lower Allen nut in the picture is the hammer spring adjuster nut. it is the same nut that you'll put the lock tight in the threads when you've got it set where you'd like.
The Bobcat are in the same family as the Royal's (AKA 400,500 and boss), they share all the same oring's, barrels and body, only the stock and triger's differ, very close but the bobcat using linkage. As they adjust the same way.
You can leave the tank on and aired up, with pressure on the regulator is fine. Make small adjustments and be sure the gun's not cocked when adjusting.
To adjust the hammer spring just turn the nut in or out with the 5mm Allen key, lock tight when happy. It doesn't take a lot of lock tight to hold the nut.
If adjusting doesn't make a difference in the FPS you have bent your pop valve. If you shoot to low in pressure you risk the chance of bending the valve. A very bad bent valve will leek air, if the valve is slightly bent the proformance of the valve will drop. In turn lowering your FPS.