Jammies to bed

I usually put baby in a fleece footed PJ or a cotton footed PJ. The temp in room is usually around 66-70 degrees. A friend was saying that a onesies t-shirt should be put under the jammies but wouldn’t that make baby to warm? How do you ladies dress your little one for bed? Once winter hit i may put under shirt under footed jammies.( will ask doc at 4 month appointment to be sure don’t wanna over heat baby or have baby to cold) also we don’t use a swaddle baby never liked it and sleep good without it