Do you wear nightgowns or 2 piece pajamas?

Both and my blankets keep me warm

Around the house, I wear pajamas (leggings, thin capri lentgth pajama pants or longer boxers with a tank top, and if necessary a long sleeve tshirt). I also have an "around the house" thin hoodie that can be layered over the rest.

When sleeping, I wear panties only. I don't like wearing any other garments when I sleep. If I get really cold then I will add another throw blanket.

Same.  If it's very cold I might wear leggings and a long, close fitting shirt that won't twist too much.  But I hate wearing anything. I just tolerate those when cold.  Rarely. I toss and turn a ton and hate things getting twisted. 

Top is a tank/t-shirt/sweatshirt depending on the weather.
Bottom is either underwear or light sweatpants, once again depending on the weather.
We don’t keep the a/c or heater on when we sleep.

2 piece pj's. I have to have my legs covered. Never could stand having a nightgown ride up on me.

I wear pyjamas with a short sleeved T-shirt, but I never sleep in the bottoms. I can’t stand anything round my legs at night.

This is what I do also.  I need the leg warmth of flannel bottoms during the winter, even in Southern California.  Could you try the type of bottoms that have a drawstring in the waistband instead of elastic?  That would allow you to loosen it to the point where the pants won't fall down, but also not put any pressure on your skin.  I have one pair of sweatpants that have the drawstring (actually have them on at this very moment) and I tend to keep it pretty loose.

Ribbed tank and cotton undies (year round).

I have a couple pairs of Soma pj sets that I wear if we have company, for Christmas morning, when I travel with someone other than dh, etc.

The waist band on these is so comfortable. They also have night gowns, shorts, long sleeve, short sleeve, tank, etc. High recommend and a great sale right now.

Soma Cool NIghts

I don’t like bare legs when I’m sleeping and I can’t handle how nightgowns twist. ]I wear PJ pants and a t shirt. I don’t like long sleeves when I’m sleeping.

We all use pretty two piece pj sets as loungewear at home.

We change from outside clothes into loungewear as soon as we come home for the day.

For sleep, we all strip down to just underwear.

I wear yoga pants day and night, or if I need to go out I'll change into jeans or whatever's appropriate.

For you, OP, I think the union suit (no waistband) idea might be a good one.

Or alternatively, you can find pajama pants that tie at the waist rather than use elastic, so you can untie them after you get into bed. Look in the men's clothing section.

Loose leggings and a tank or t-shirt snd socks. I can’t stand my feet or legs to touch each other at night (weird) so I keep them covered. In the summer time I do wear Capri leggings. I used to wear night shirts of cute two piece sets but switched as these are more comfortable.

I have so many pairs of pajama pants that I have to have two drawers for them. I also have matching 2 piece sets. I have winter ones and summer ones. When I'm sleeping alone, I tend to get cold, so I have thicker pajamas for that and thinner cotton ones for sleeping with DH or during summer.

I occasionally sleep in underwear or nude but only rarely, because I don't like when I eventually warm up and my thighs stick together if I get sweaty (sometimes I get hot flashes, though I haven't had any in a few months). And I prefer to sleep in a sports bra because these implants are very heavy compared to what my breasts felt like! I like them secured.

I sleep in undies and a tank top or t-shirt. Sometimes in winter I will wear two piece PJs while I am watching TV, then take them off when I go to bed.

I don't know how people wear nighties / nightgowns. On the few times I've worn one, it drove me nuts because it kept bunching up - so uncomfortable.