I've seen floor joist methods ... cutting holes into icf, or using a concrete ledge, steel wedges, etc. but since ICF move up and down in the concrete pour, the icf may lose their level and height? What solution works the best?

The best ICF blocks do not measurably compress or move up and down during the pour. There are installers out there that believe that this simply cant be avoided but such is not the case. Regards.

ICF can compress slightly, some more then others. I attach my rim board prior to pouring, we check it after the pour and the rim is within a 1/4" around the entire perimeter, a 1/4" falls within an acceptable tolerance. I can assure you by the time you take into account bumps in the floor from top mount hangers, sub floor adhesive, rim slightly larger/smaller then the joists, swelled/delaminated plywood from weather exposure...the 1/4" is nothing and goes away.

If it's worse then a 1/4", pull the rim, bore the AB hole slightly larger and reinstall with a tighter tolerance.

I've used both the Simpson and ICF Connect products. Saves time and lets you make a height adjustment because you install the rim joist or in the case of the ICF connect product the actuall joist after the pour. The Simpson product is $12 to $15 per set with normal spacing of 4 ' each and the Icf product is less but you use one per joist while negating the need for a rim joist. So the cost versus time element is the reason I choose to use these products.