Wanted to address the first two from a friend's experience - these are absolutely not true.
They are able to work 4 hours a day remote (2 hours per job) and get good reviews. Some days happen to be a full 8 hour day, but they're rare.
Meetings for junior positions almost never conflict when the junior has less than 3 meetings a week. It sounds like it would be common, but turns out it's rare.
- you're assuming that the schedules will magically align - they probably won't
- if either company thinks that you're working full time but you aren't, I wouldn't be comfortable with this from a purely ethical point of view