I have an ~110 GB world and the bluemap took up the entire 512 GB SSD. For the sake of both disk use and performance, can you add a config setting that turns off generation AND rendering of the hires map entirely?

There is already a setting save-hires-layer in the map configs which does that if you set it to false. It will still render the highres-models since the lowres-models are dependent on data from the hires-models but the hires-models aren't saved anymore.
-> No performance improvement but a huge disk-use improvement.

BlueMap is a 3D-Map, so the 2D-Map options are very limited right now. There are plans to improve on that end, but that not yet happened.

Also please use our discord for support, questions or suggestions, GitHub issues are not the right place for that. :)