Figure out which one you respond to best, higher reps with less load or low reps and higher load. You can use any rep scheme you want within reason as long as the volume is high enough.
If you- respond better to higher reps and less load and want to use a lower rep range with a high set count- you can still do this easily, just keep the total VOLUME high, meaning a lot of sets of lower, high quality, reps.
If you respond better to lower reps and higher loads- you can still use highish reps, just do it with rest paused/myo rep/cluster type set rep schemes, and focus on total poundage moved in those few sets.
Likely one of those will be more OPTIMAL for you, and the other will still "work", assuming youre consuming enough protein and total calories. If you can think back to which one you respond the best to, pick that one.
If youve been on 5's for a long period of time, just switching up the rep scheme can bring you out of stagnation. Vary it from day to day, week to week, whatever, but use 3s and 8s etc. for a while. That by itself will often take you out of a rut if youre stuck in one. Either way, youre not going to build any significant amount of muscle tissue if your diet isnt on point, so get that fixed as well.