There is on-going discussion / debate on another site about these items. I've maintained these two points.
1. The panties should go on top of the straps. I mean, that's what I've seen in most, ah, on-line photos. (There are occasional exceptions I've seen, however.)
Unfortunately, at this late stage of my life, I don't know any women I could ask about it. My ex-wife never wore garters, although now I wish she had. (Not that it would have saved the marriage.)
2. I think there are women who still wear garters and straps just for the fun of it, because it makes them feel sexy, or whatever.
That leads to one more question.
3. Thigh-high stockings without straps are pretty popular now, especially in warmer weather, correct?
Here are my thoughts, but I'm no expert. My Mother wore a garter belt and stockings quite a lot back in her day, and her panties always went over the garters. I'm positive it was so the panties could come off without disturbing the garter belt and stockings. On the rare occasion that I wear them, that's how I do it. However I've also discovered that a garter belt and stockings alone, without panties does a sufficient job of attracting attention to the area I'm trying to feature, and panties aren't required at all. Yes, I absolutely only wear them for fun, but thanks for reminding me how fun they are! I don't think thigh-highs are popular at all, again not unless it is for a special sexual adventure.
I love wearing garter belts and stockings usually with panties over the straps so that I can thumb them down
mmm...Yes! Love wearing garter belts and stockings, especially silk ones... usually with the full suspenders. I even where them to work ( pre-COVID), as I feel soo sexy in them. Panties or thong at work, of course. If out or playing, it depends on the experience I'm looking for. ;)
I don't like any of them. No garters, no stockings, no panties. Less is more for me.