What matters is that you know where the pellet is going to hit at the various distances you plan on shooting. Some guys get very serious into the apps like Strelok and Chairgun. In fact, it is quite common to see guys range a target in FT and then break out their phone for it to tell them how many clicks or where to hold. Personally, for precise shooting like FT, I like to actually shoot my rigs at all of the ranges to find out how many clicks it takes or where I need to hold if I am not clicking. I typically shoot at every yard from 10-20, every 2.5 yards from 20-30, then 5 yard increments on out to 55. Not only does this give me the confidence of KNOWING where the pellet will go if I put in 10 clicks and hold on the crosshairs at x yards, it also provides me plenty of practice and the enjoyment of simply shooting my guns. And all the up and down moving my pellet trap simulates up and down moving from one lane to the next so helps me deal with the effect of momentarily increased heart rate. After a couple years of doing this, it just dawned on me this week that if I had another couple pellet traps I could get a lot more shooting done in a session and a lot less pellet trap moving (laughed at myself for not realizing this sooner).
I do agree with the above statement that working with only hold overs is less complicated than hold overs and hold unders. However, I have heard a member of our club give a pretty compelling argument for hold unders by suggesting that cant errors aren't as pronounced because everything is kept closer to the center of the scope.
A zero somewhere near the middle of the ranges you think you'll be using the RX2 for is as simple as it needs to be. That zero will become a range from x yards to x yards where you don't need to click or hold over, closer will require hold overs and farther will require hold overs.
Having said all that, for hunting and pesting at ranges further than 55 yards, I do like to use Strelok.
(I have a recently acquired .20 RX2 that I am assessing for possible use in Open Piston Class. So far, I am quite impressed with it's accuracy and I really like the quick shot cycle.)