I would say you are describing very much what the Yoga District class is - I take Tuesdays and I really, really enjoy it. I posted here about which classes people recommend, and this was one of them (people said Flow was more difficult since I'd never taken Yoga before).
Brittney takes a pulse of the group and when it seems like people are dragging, she definitely makes it a more relaxing class. When people are generally feeling good, it's harder. There have been times when I've been sore (in a good way!) after the class. So it definitely depends on how she senses the class is feeling.
It has also gotten more busy - Tuesdays are pre AND post natal, so sometimes there are children. I can't complain because it's advertised as such, but it is a little difficult to concentrate during relaxation times when there's crying. But the flip side, I have to work to block it out which is part of the benefits of the class (if you're hoping to use some of it to prepare for natural birth...right??). So I try to use it as a positive as best I can, and I know it's a great thing to have an evening post-natal since most seem to be during the day so if you work, this class is helpful.
There are harder movements like lizards, squats, etc that I don't know how very pregnant women do! Pikes, Dolphins, and not sure what else because I don't know much about yoga.
We do the intro (name, weeks, if you know if you're having a boy/girl), what issues you are having. Brittney is VERY open, sweet, and gentle. I like her class better than Tranquil Space (but I also enjoy that class, too, just in a different way). I've never done thursday's prenatal because it's at a bad time for me.
hope that helps!