@orlandodoncarlossalina First of all no, you being fresh doesn't make it a more reliable metric than you not being fresh. As long as you are using them in a consistent scheme it doesn't matter.
Second as to the RiR estimation problem it won't matter once you set up a progression scheme and let the autoregulation kick in.
Say you do 4 sets of whatever, you can guess a weight that you think is your 12 RM then do 3 sets of 8 and AMRAP the 4th set. If you hit 4 reps over your sets across (so 12 reps here), then increase the reps by one (so sets of 9 next time).
[Some people will argue here that the average RPE is too low in this scheme. I disagree but it doesn't matter you could just do the same scheme but start off with sets of 9 and make your goal +3 reps over that, or whatever.]
This is what I do for all my lifts and I think it works fine. I might do it differently for barbell compounds but I don't do any of this right now.
Second as to the RiR estimation problem it won't matter once you set up a progression scheme and let the autoregulation kick in.
Say you do 4 sets of whatever, you can guess a weight that you think is your 12 RM then do 3 sets of 8 and AMRAP the 4th set. If you hit 4 reps over your sets across (so 12 reps here), then increase the reps by one (so sets of 9 next time).
[Some people will argue here that the average RPE is too low in this scheme. I disagree but it doesn't matter you could just do the same scheme but start off with sets of 9 and make your goal +3 reps over that, or whatever.]
This is what I do for all my lifts and I think it works fine. I might do it differently for barbell compounds but I don't do any of this right now.