I always allocate about 90 min from check in till I walk out the door, which includes the time to wait on a table, the photo op and eating, etc. That is probably about 10-15 more than it takes but it's never too little.
Nope, no one can tell you what Princesses you'll meet. Can tell you who won't be there, and that's Belle. And Cinderella will only meet you downstairs for photos, not up at the table.
Otherwise, pretty much anyone can be at the table. There is no such thing as a "regular" it's all on who is available to work that day and it varies.
It is usually 4 different Princesses