Well, if you're aiming to optimize for speed, not marking mines in the first place is faster :) The game ends when you uncover all non-mine squares, so only those squares need to be clicked.
True, true. I've been trying to play loopy without marking any edges, and it's way way harder. I think there's still an advantage to going fast at the sort of low intermediate tier where you're still using markers.
You mean without clearing any edges, right? As in you only left-click edges, not right-click them? I used to do that too. I haven't played in over a decade, but IIRC it was relatively easy to do that on the honeycomb and octagonal types (because most edges need to be left-clicked) and on the triangular type (because it has the fewest edges per tile).
And yes, loopy is a great game.