You will be fine, the a321 has ample sized bins, in comfort plus you will board early enough to find space, many planes have extended bins these days making for even more overhead space. If for some very odd reason you can’t find space your bag gets checked to your FINAL destination. I think dl has slightly smaller bag sizes because they have a very large fleet with tons of different size planes and bins but they really don’t much care at the gate and your actual flight is on a plane with decent size bins

also, you will probably hear a bunch of dire announcements about overhead space and bringing your bag to the counter to check it in at the gate, ignore said announcements, you are in an early boarding group, half the time there is plenty of space even with the dire announcements