The polishes w/o fillers I'm currently using are the Menzerna triplets, 3M MG, and Pinnacle's SMR and SMR Advanced. All have been compatible with Zaino for me, and that's a fairly good test of being filler-free.
SSR2.5 (swirls/spiderwebs), Menzerna IP (swirls/spiderwebs) and Menzerna FP (spiderwebs).
But I often use 1z UPP (which I believe has some fillers?) for some severe work and follow up with a filler free polish to burnish the paintwork (such as FP).
I too use 1Z Ultra/Extra for some tough stuff, it leaves wax but since it also leaves micromarring (and not always so micro!) I don't mind. It really *does* cut, so it's not like the wax distorts what it's accomplishing.
The recently discontinued 3M PI-III RC and MG (05933 and 05937) have been my standard, filler-free polishes for ages. By hand/PC/Cyclo/rotary, they work great.