We always played that a 20 always hit but that it was only a critical hit if you *could* hit with a 20. That way some things that should be darn near un-hittable had a chance to be hit, but not a chance to be *ended* with some catastrophic effect. Taking out a big-bad with a lucky roll was never truly satisfying.
We also used the "Good Hits and Bad Misses" crit tables from Dragon Magazine (Dragon #39, 1980)... though we didn't use the more complicated system they used. But if I was to play a 1e-2e game now, with a VTT to work out the calcs and auto roll the percentage, I *would* use their system since it scales based on how well you hit and how well you can hit... addressing two of the core problems of a d20 crit/fumble system.
You can read the article here: https://www.superdan.net/download/bl...9-CritHits.pdf
Looks like the PDF is from the best of Dragon Vol. 5 (laid out differently from the earlier article.)
All of that said, I do think any Critical/Fumble system you incorporate into the rules does need to be a "House Rule"... preferably with modifiable tables, etc. I've found that many old-school gamers have used different crit systems. Heck I just pulled out my dog-eared photocopy of the Dragon article that I would hang on my DM screen and I have notes all over it for modifications that were made for our game... and low-and-behold I see that we did, at some point, modify the Crit system when needing over 20 to hit. It prompted a percentile roll:
1-50 Regular Hit
51-80 Double
81-95 Triple
96-100 Roll on the Crit Chart
Not sure how often we used that house rule though... I would probably poll my players for its application to see if it held up for today's sensibilities... *shrug*