On the original subject: I playtested Pathfinder 2, and I kickstarted Nimble. Both have a 3 Action economy, and I find that while I love the idea "on paper", I absolutely HATE it "at the table". I just find that players (my players at least) can come up with TWO actions that they want to do on their turn, or they can come up with FOUR, but they struggle to find the 3-action sweet spot.
At least they do what I would say is too much of the time.
In both those games, I felt that we were always either reigning in the 4x actors, or waiting on the 2x actors to pick one more thing, that it really slowed the game down.
I'm interested in an approach like
@mearls' Moldvay, where there is a strict (but not too strict) ONE action economy. No Bonus/Minor/Swift action, either. The occasional free action is granted by special abilities (somewhat like how "Extra Attack" gives you 2 attacks in 5e, but it doesn't give you two attack actions.
Take your turn, move on.