I've always laboured in a nightie as it's been night time. And worn pjs after. Big underwear and huge pads :) but anything as long as your comfy x
I've always laboured in whatever clothes I had on, then wore a bikini towards the end whilst in the birth pool (string tie bottoms are very easy to take off :) )
Then after birth I've always liked loose pants or shorts, big but firm fit undies to prevent leakages (first night after birth I've always worn an adult nappy so I can sleep in peace), and a relatively tight breastfeeding singlet to hold everything (floppy stomach and sore boobs) in place. (Breastfeeding made my nipples super sensitive even from day 1 so that anything that rubbed on them hurt, I couldn't wear loose tops that would move, had to wear tight stuff or a bra as they just stayed in place well. I would have hated a gown I think...)
Please buy gown to be comfortable after delivery especially when u will be having visitors. Buy sleepers mommy, its gonna be it comfy shoes even at home