[ymu]

If all of your opponents were playing optimal ICM strategy and unexploitable HU strategy, then no - you can only find an edge in either advanced ICM plays (which are rare), manipulating your opponents (which can be difficult) or in picking up/not losing chips early.

Otherwise, against average opponents, I would think curtains is about right. Your edge doesn't come from you playing better - you can play optimally because this forum tells you exactly how to do it. Your edge comes from making fewer errors than they do.

Obviously, the edge you can get at different stages depends on the level you're playing at. But then, as you move up in stakes, you develop more skills to find more edges. Advanced non-ICM plays and manipulating your opponents is needed at the higher stakes, but lower down more fundamental skills serve well enough to find a sufficient edge.