Since the PAC 12's collapse, 10 former members have been competing in 3 Power Conference leagues. They have, as a whole, struggled mightily.
Here are their records vs new conference mates (games vs former Pac12 teams have not been counted):
Oregon 6-0
Washington 2-4
USC 2-4
UCLA 3-3
vs B1G total - 13-11
CAL 1-4
Stanford 1-5
vs ACC total - 2-9
Arizona 0-5*
ASU 3-2
Utah 2-3*
Colorado 4-1
vs B12 total - 9-11
All combined - 24-31
Oregon and Colorado are carrying their former conference mates. Without those two, the total lies at 14-30. ASU is the only other team that is above .500 thus far.
*note that Arizona and Utah have played 2 games vs their new conference that did not count as conference games, those have still been included.