Hello there, I am a Twink enthusiastic and would like to talk for a bit!
Gear customization’s main advantage is that you can make many spec and classes somewhat viable in lower level PvP, allowing more diverse playstyles even for those that are leveling and have only a few enchants.
Legion’s templates made twinking impossible in it’s common acception - but I personally liked the satisfaction of winning teams by using some tactic, not only brute strength.
The power advantage that twinks have nowdays are way smaller than what it has previously been. It still is quite noticeable nonetheless, with an difference of about 30-60% between a reasonable geared character and a twinking, I would say.
Twinking Is just a game style and it should’ve been deterred. My proposal is to further decrease the power difference would be to increase the kind of items that drop from the lowest level dungeons (so that you can quickly have a nice trinket when leveling, for example) and to also give spells more quickly across the classes, to avoid some of them having almost none of their necessary kits at some brackets (even if it means bigger level gaps between spells being given).
If possible, also buff some of the profession made items so that levelers can have more gearing chances (the various stat squishes heavyly affected some of those items).
“Buff the levelers, don’t nerf the Twinkers”.