Ive trimmed on small twists and had decent results.
I tried trimming on larger twists last month and JACKED my ends up...uneven when straight but decent looking when curly, so if you wear it curly then no issue trimming on big twists then!
Trimmed today on straight hair, I flat iron, then pull back in a low pony, then slide the ouchless band straight down w/o moving my head or moving hte band to either side, then I snip how much I want. Then I do the same on each side.
I copycatted the technique of a woman in a YT vid. I couldnt find that vid now if i tried. Maybe someone else knows it... she was a white woman with super long stringy hair.