I tried padded tights but I'm very particular about my pad and use different grades of pads for different types of rides. So I quit doing that and now only use unpadded tights over padded shorts. That's warmer and less expensive as the tights last a long time. No visible butt crack, ever. Also, no fit issues. Any brand works, though I usually use PI.

The downside of knickers and knee socks is that there's no way to keep rain water out of your shoes - it wicks down the socks. With tights, one puts dry-suit leg seals above one's booties, right on the bare ankle, then zip the tights over the leg seals. Dry feet.