> Traditionally, when working two part-time jobs, you aren't typically doing both part time jobs simultaneously

Nobody is doing two jobs at once. They can only take one ride at a time. They simply alternate ate a higher frequency than other jobs. Why would this frequency have any effect on how they are treated?

> While I support good wages for drivers, it is unclear who pays the good wage -- Uber, Lyft, or both, or half each

They get paid by the company from which they take the ride from. Whoever they're working for at a particular time, for those particular miles, is who pays the rate.