@taylormccue Voted other to say: I'm currently struggling with this, and I keep ending up back at 16:9 and ideally an integer factor of 1080p. If you're doing any sort of pixel art, it's most likely to look best on most displays. 720p might be the sweet spot. TVs, Switch, most monitors will handle 16:9 well. Even for outliers like Steam Deck (16:10) you could just letterbox.
My games are usually chonky pixels, so I'm at like 640x360 (1/3 of 1080p) for crisp scaling almost everywhere.