I'm curious how you or your DM runs critical hits in your game?
In my BX/LL game, a roll of 20 indicates a critical hit and the PCs can double their rolled damage. We also play with critical fumbles. If PCs roll a 1 they then roll on a d8 sub-table for mishaps.
There seems to be more consternation about critical hits in more recent editions. This is just another example of rules bloat to me.