I ignore the class system [a ***'s breakfast] and follow the cash and the trainers head-space. I couldn't care less about the class of a race and nor could most trainers [type of race like open, mares, fillies and mares etc. sure, but not class level]. They are interested in the prize money.

The more the prize money of a race the better the horse has to be to win it [simple isn't it?]. After eligibility, trainers look mostly at the prize money, they then know what 'class' [or field strength] they are up against for any of their horses.

All things being equal, I'll back a horse who has won a $22k C1 against a horse who has won a $12k open handicap, welter or whatever, every time.
I couldn't give a fig about the class system, I've got better things to do with my time that getting lost in the mumbo jumbo land the class system has turned into. I Follow the money guide and handicap a horse on the prize money it has competed for and how well it went doing so.