DnD Head Canons

[PairO'Dice Lost]

Then why is Lolth pushing the baroque social structure? It doesn't really matter if she's imposing a Lawful social structure because she thinks it's fun. You've still lost any predictive power alignment might have had when one baroque backstabbing nightmare is "Lawful" and another is "Chaotic".

I think it's possibly like the difference between a Baatezu courtroom, vs the Abyssal courtroom layer Woeful Escarand. The baator court is going to be cruel but it's going to follow the rule of law, whereas the abyssal court exists as a mockery of the rule of law and is openly corrupt.

Pretty much this. It's the age-old question of Who are you when no one is watching?, that is, if you take a bunch of drow out of Menzoberranzan or remove Lolth's influence on their society (permanently and in a way that they all know it's the case, not temporarily and in a way that her priestesses try to cover it up like during Lolth's Silence), what does their new society look like?

This is actually something that happens in-setting, with Chaotic-but-not-quite-so-Evil drow leaving the Underdark and joining with followers of Eilistraee, a CG goddess. The Church of Eilistraee is still a matriarchal theocracy, but it has a very flat hierarchy, different settlements (and groups within those settlements) are only loosely interlinked, and male and female drow can take on any desired role (and males can lead, though mostly they don't), a far cry from the traditional strict hierarchy with strict House associations and strict gender roles--so, much closer to other Chaotic societies like the moon elven cities or orc tribes than the byzantine Lolthian drow culture.

I have a head cannon to share. Since I've played most editions up to 3.5, this is how I see it all as being the same world. Basically as time passes, the laws of magic and whatever it is that governs the powers available to the living people/creatures changes and evolved over time. That would explain how even PC classes started with minimal capabilities and we're very limited in power, then developed immunities, resistances, faster actions, etc.
The timeline as I see it:
OD&D - Early Dark Ages
AD&D 1E - Transition of Dark Ages to Early Renaissance
AD&D 2E - Early Renaissance
D&D 3.0-3.5 - Mid Renaissance
D&D 4E - NEVER HAPPENED - or possibly a past timeline off of the d20 Modern setting
D&D 5E - After Renaissance, maybe just before what would have been our Industrial Revolution
*Eberron in play is like adding the Industrial Revolution to the edition's timeline

I've been considering converting some older edition magic items but making them with no change if possible and tagging them as "Heirloom" or "Ancient" just to see how it goes.

I do something similar in my games. For instance, the thing where 1e psionics only involved random wild talents, 2e psionics had classes but required some innate talent, and 3e psionics allowed anyone to train in psionic classes, and in AD&D psionics was different from magic by default but in 3e they're transparent by default? In several of my long-running settings that survived long enough to go through edition changes (and under my own take on FR's history), the former is due to psionicists reverse-engineering and codifying psionics in the same way that wizardry was first developed and the latter is due to research collaboration between psionicists and arcanists to unify their magical traditions. Scholars in-setting know that psionics used to work differently and will talk about So-and-So's early experiments in awakening psionic potential or Such-and-Such's Theory of Thoughtform Universality or the like when discussing the history of magic/psonics interactions.

Several of my longer campaigns have involved time travel to some extent (either short jaunts into the past or areas that were brought forward in time), and when that happens I've broken out older-edition rules for a few sessions and/or converted things to newer edition rules to hammer home the difference. The very first time I did this, I secretly converted all my player's characters from 3e to 2e beforehand in preparation for an upcoming temporal jaunt; when they stepped through a time portal (thinking it was a regular portal) and one of them asked to make a Knowledge (Planes) check to see if they could figure out where the portal sent them, with a perfectly straight face I responded "There's no such non-weapon proficiency; perhaps you mean Portal Feel or Planar Survival?" while handing over their 2e sheets, and it really drove home the "we're not in Kansas anymore" feel of the adventure.