Graybeard
I assume you have access to "flying together.com" and have read the parts about baggage checks and such. If not here's the international info:
"International travel. International checked bags will receive a "status pending" bag tag and will be boarded on the aircraft when the pass rider is cleared for the flight. If the pass rider is not cleared, his or her bags may be reclaimed in the baggage claim area."
The rest are sent onto their destination on Mainline UAL flights and on the RJ flights you gate check them and pick them up at the gate.
"One carry-on bag
One carry-on personal item
Two checked bags, up to a maximum of 70 pounds each"
All this is the same as it's been for at least a decade.