Disclaimer: My comment is just a superficial note on the topic and does not represent a qualified in-depth summary.

Yes, indeed. They would be most useful in rural areas, where public transport is not sufficiently present and could therefore replace cars.

But those are the areas, which are not as profitable as cities. There, decent public transport options often exist, which is why they often replace walking and thereby increase emissions.

But that also depends on particular individual factors like the electrification of those public transport modes.

There is some reaearch on this, for example:

https://www.itf-oecd.org/are-e-scooters-good-or-bad-environment

https://doi.org/10.1016/j.trd.2020.102680