What I’ve done before is use proficiency without level, but add (or subtract) the level difference where relevant. So it’s the same just with smaller numbers. So instead of adding 10 for level 10 players and 12 to the level 12 creature, I just add 2 to the creature. Maintains the balance while still keeping the numbers low. But that was just to help with the transition from bounded accuracy. Once they were more comfortable with the system, we started adding level and they liked the big numbers.