990 EVO Plus vs 990 Pro (I have no idea what's HMB)?

Hey guys, I have Samsung 970 EVO 500GB, that what I believe has DRAM.

990 EVO Plus is the first NVMe that does not have DRAM (correct me if I'm wrong). Will there be any performance difference between PRO and EVO Plus, because benchmark shows negligible difference. And also, how does the HMB play a role in all of this?

Does that mean that 970 EVO that does have DRAM would actually transfer faster up to 2Gb of data than 990 EVO plus that does not have DRAM cache?
Did Samsung cut corners on 990 EVO Plus?

Cheers!