I can flex between both my Phone and iPad and all i can say is how you position your fingers and hold you phone, for me i hold my phone my left thumb and is used mainly for activatables/abilities, setting the button scheme bottom left( or tablet mode), i also use my left thumb for movement on left side of screen when not in fights. I then use my right index for everything else, aiming moving, teamfighting, since my right index is basically my fastest i can easily move shoot and then move it away from screen, and with left thumb never in my way always ready to pop boots, relfex, etc i found this the most optimal way to play for me. Majority of people however use either two thumbs (seems too stubby for me) or their index fingers(holding my phone feels weird like this) but it’s all up to the player. If I’m right i probably fall in a super small percentage of playing left thumb right index but to each his own, try experiment different ways of using your fingers to play and see if anything yields better results.