The biggest thing this year is that you CANNOT try to execute a bunch of skill moves in traffic. The ONLY time I personally use R1 (and you have to hold it, not tap it) is when I am up late in games when the CPU will use the coach adjustment to strip ball. When using a RB, when I fumble, it's usually because I tried to make a juke/spin too close to the defenders. When I see people on social media crying about fumbles....9 times out of 10, it's because they were foolishly trying to chain together a series of moves in traffic. My rule of thumb, if I have one defender in front of me, I'll try a move (unless ball security is critical). If I have more than 1 defender around, I will just use the left stick.
With QBs...slide...slide...slide.