A glitch is sort of like a spike in a program or device. It's not a big deal, unless they keep coming back. I think 2 discs is not a recurring feature yet.
The P-CAV is a writing technique and means Partial Constant Angular Velocity. P-CAV is a combination of CLV and CAV.
The transfer rate increases until the drive reaches it's maximum speed (CAV). From that point the drive will slow down and the transfer rate will be constant (CLV).
Because P-CAV drives reach their maximum speed much sooner than CAV drives, the average transfer rate should be higher.