What does your baby sleep in?

I'm in california and we had our first colder week (cold for california that is) its 70 degrees in my house right now and if I dont put on the heater I expect it to get to 65 probably tonight.

My son has been sleeping in only footie pjs. Before he slept with a swaddle and short sleeve onsie but he gets onto his side now and the swaddle limited him. Hes 12 weeks now.

Im contemplating if he needs like a onsie underneath his pjs and socks or if it will be too hott. I do have sleep sacks but I never used them. With the way he moves I dont think its wise?

At a loss. FTM.. Lol