Always under your tights as bacteria is likely to be increased wearing the tights under the panties. I use support wear and still have the panties under the tights (if I wear them) then the support wear and stockings. More air feels fresher. Wearing tights when it is very cold.

I prefer to wear my panties under pantyhose. To be honest, I prefer stockings and a garter belt though

I never wear panty hose, mostly bare legs or tights when its chilly,in which case wear my knicks beneath the tights.

I like to wear my panties under my thights.

So, I wear opaques for warmth but have panties under and also a body to prevent them from coming down while doing housework or gardening. The thing is the tights tend to roll up and are somewhat annoying. But if for social events or non-busy days the stockings always get my vote with the corselette for my lower back problem. I like stockings for the air area at the top. Tights are fine and keep you warmer. Panties, tights and body or support pants. I hate that tights feeling that you know they are rolling down, sorry from the waist. But do not allow them to be in contact with your genitals as it is most unhealthy a feeling. Panties keep you confident.