You can’t over stabilize as they say.
That statement is from Berger's Ballistician, Bryan Litz whom also works presently for Applied ballistics. Which is misquoted way more than one would think. Bryan Litz's statement is basically is you can't over spin a
quality bullet .
I will purposely avoid the rabbit hole of what is a "quality" bullet. But will say his basis of his statement is a Perfect bullet, which none of us buys, nor can we obtain yet technology is just not there yet.
Reality as in actual hands on experience with the 1-12 and the 1-7 twist, to answer the OP's question,
if using cup and core bullets, 62gr. (heavier / longer is better). If
monolithic, depending on the length it
maybe a 55gr. The reason for the this is the density or rather weight of the lead itself, a monolithic bullet needs more mass to equal the weight hence usually the bullet is longer which requires the faster twist.
Actual real world experience is yes at short ranges (under 200yards) the 55gr may produce some really good groups, but enter a shot needed beyond that it fails miserably. What basically happens is precession takes over. Causing erratic dispersion (large group sizes) at effective longer ranges.
Now many will jump on here stating their 1-7's will produce great groups yet NEVER shoot them at 300, 400 yards and beyond.
So if ones desires to prove their point I would suggest going to the range and shoot a 5 to 10 shot group at 400 yards and report back with a target. And no cherry picking of targets.
Since the interception of the M16A2 with it's 1-7 twist, the military of the US has even written NOT to use the 55gr loading in the A2 and newer because of this. It is fine for use in the M16 and the A1. I've seen shooters whom regularly qualify as Expert either fail to qualify or barely make standard (Marksman). Change to the correct ammo and they will qualify as normal.