I've the airflex stealth (shoulder, spine, chest) protector. It's pretty good for ventilation.
The focus is on spinal protection. Shoulders are minimal and it's VERY easy to get on / off.
A 661 top I have with only shoulder protection is like a plastic bag by comparison. It's like a compression top but with integrated shoulder protection. Good but not.
I've also got a 7idp one, better coverage of the shoulder but the spine protection is more cumbersome. It does come higher up the spine though. It's a PITA to remove once you're hot and sweaty.