Cass, I've got all blasts in the freezer, doing my second HRT FET now.
I had Pregnyl support shots when doing my IUIs and IVF, I think it is my clinic standard, and also had to have pessaries as well for low progesterone in a couple of cycles.
My clinic does a follow up BT to check hormone levels a few days after ET, & guess then adjust accordingly. Can't say anything specifically, because I just do what they say & hope for the best. But I do feel that they do cover all bases.
It seems I have low hormone levels so they do keep a check on that & adjust whenever.

Hope everything goes well with you.
There are lots of people in here with the knowledge that will help you.