I've been observing for over 40 years, almost all of it with refractors. The lions share has been with a TV102 and now I've had an NP101 for several years.
I've read Ed Ting reviews of really good refractors similar to the TV102 and NP101 getting up to really high magnifications and after some pretty good seeing earlier this week I've decided I can get ~300X with my NP101 but the view in my opinion breaks down above that and I'm not certain it was the scope but I'm wondering what others have experienced. The eyepieces were Nagler 5mm and 3.5mm, both with the same 2X power mate.
I have an Obsession 15UC coming pretty soon but until I get that, I have to judge the seeing by how much the overhead stars twinkle. Seeing wasn't "best ever" but definitely "very good".