The Garmin Varia rtl515 works well for me as a solo rider. It has various settings, but I use the flashing mode since nobody is on my wheel. Some of my other rear lights do that, too. The Bontager Flare is nice. But the Varia has a feature I use more and more: the radar feature. Granted, it needs either a Garmin head unit or your phone app, but it is great at picking up traffic behind me. It gives visual and audible cues. I do use a mirror, but the Varia is very accurate.

Mike