Depends for me. I find I can repeat an ma stroke faster than an im stroke, so i'll do that generally. If I need more speed than I can get with repeated am strokes, and if the bassline allows, I like to alternate pi pm.
If I can't get p involved (Rossiniane #3, e.g.), then it's about holding a little tension and practicing a quick extension to prepare for the next stroke. I do that by playing super staccato in the right hand, immediately pre-placing ma after the previous stroke (a technique I use for a lot of fast right hand passages).
Re LH, I don't try to think of it as a single smooth, fluid gesture, as that makes me less accurate. If you are relaxed, quick, and accurate, it will look like a single gesture, but that thought process gets in the way for me.
Taking a stab here, but is it Rossiniane #3 you're asking about? I hate that passage. Except when it works, then I love that passage.
Amateurs practice until we get it right; professionals practice until they no longer get it wrong.
1999 Dake Traphagen (spruce)
2008 Dake Traphagen (spruce, double top)
2010 David Pace (cedar, double top)
2019 Antonius Müller (cedar, double top)