My goal for the first few super ascensions is to pick up 1 new legendary each time through. That means I'll be selecting an additional artifact slot until I can upgrade to a second insane.
That's an interesting idea. At first listen seems like a balance between wasting AP vs wasting digs, b/c the game forces you to choose to prioritize AP (+25% buff) or digs (+1 artifact keep) and whichever one you don't pick means you waste the other (have to clear more levels to earn the same AP vs throw away artifacts b/c you don't have room to carry them over).
But at second glance, it's actually just favouring digs, b/c you'll spend at least 4 SAsc cycles without additional AP, so you'll be spending more time redoing levels, but digging the entire time. However, these digs will be at slower speeds (no phase 4 +50% Faster Digs). But offset with Legendaries that will turn into an Insane and free up 3 more spots going forward.
Compared to the +25% AP strat, which means 0 new artifacts each time and tossing any digs you may do that SAsc, but it also means quicker SAsc's = more artifact carryover slots (more quickly).
Hard to say which is better ... but maybe the artifact option will feel better while playing.