The fabric is silky soft cottony and the seams and waistband are tight fitting - I am 5'5" 130lbs 37" hips, smallish bum and muscley legs and got a size Small. I was worried it would be too tight getting a size small and that it might have cutting feeling seams but it's snug enough that I won't worry about leaks and doesn't leave indents on my skin.
My flow is medium heavy for 2 days (normally use about 4 tampons) then very light and the underwear was sufficient absorption for one heavier day or overnight at a time. I wish I had a second pair to alternate while the other is being washed. It becomes a bit smelly and too damp feeling for my comfort to wear for more than 12 hrs. I didn't need the booster pad but maybe it would help if you want to continue wearing longer?
These days I wfh and I'm not wearing underwear very often so the fit was my key concern and it took some getting used to ;) I'm so glad I took the plunge to switch to a sustainable period solution and support an ethical brand.