in 2e, its a pretty big difference. A failed stealth check bumps down your stealth status to "Hidden" (What was that noise? Who's footprints are these? etc.), while a crit fail makes you full on "observed" (Tony Tony Chopper style.)

The Assurance: Stealth feat is the lynchpin in many a clunky fighter's exploration kit, since it will pretty much never critically fail, giving them time to hide somewhere or get help from a sneakier friend.

Isn't that usually a Session 0 agreement? If the campaign uses crit fails, then yes.

Also: best mechanic I've heard of for crit fails is the player describing the failure. They're going to come up with something better 90% of the time.

Sort of since what the DM says ultimately goes, but no - a crit fail means your effort just fails no matter what. Now, it may also mean that your acrobatics check ends in you slipping on a banana peel and breaking your back, but it doesn't have to be dramatic.

So, crit fail means that no matter how skilled you are, you have a 5% chance of failing anything you attempt (without advantage, lucky, etc. anyway)