I have been a bit paranoid when ripping that if I am using too many other applications at the same time, when the CPU pegs out at 100% or even comes near it, I am afraid it may mess with my encode. Therefore, I generally try to kick off a disc encode with EAC while I am going to be away at lunch or perhaps viewing or editing a document or two - but certainly not anything that would be processor-intensive.
I have not had issues with all-in-one jukebox rippers back in the day, but I have long since switched to EAC and it takes longer, but worth the effort...
I use test and copy always, but will sometimes fluctuate between secure or burst drive settings, if that helps.
Are glitches in my rips possible or likely? If so, would they show up in a CRC mismatch for the test and copy function or would I maybe not know about it until I listen to that part of music later on?
An error while ripping would show up in the EAC log, and an error while encoding should result in the encoder giving an error message.
Most encoders are rather sturdy however and just tend to run slower if they get less CPU time, and I've found that if something else steals CPU time during ripping it mostly just slows down EAC. I have yet to have CPU usage to be the reason for a bad rip.
I have noticed some drives can return more errors when the CPU is loaded (drives on DMA), Plextor PX230A if I remember was one of them.