UP0001-OCOP46756_00-0000111122223333.pkg is used to copy games and homebrews from hdd external to internal.
UP0001-OMAN01234_00-0000111122223333.pkg and UP0001-OMAN46756_00-0000111122223333.pkg are the same software, the only difference is that UP0001-OMAN01234_00-0000111122223333.pkg will replace any previoous back manager have the code name OMAN01234, and UP0001-OMAN46756_00-0000111122223333.pkg will replace any previous manager have the code name OMAN46756.
So, if you have a backup manager liek rogero or any other one, you can install different codename version of the open manager to have in the homebrew list 2 open managers.
so if you install the 3 packages, you will see 3 applications, where 2 are the same (Open Manager 2.1I-2. and if you install later an anpplication which have the same code of open manager (usually OMAN1234), one of your installed open manager which have the same codename will be overwritten, and the other still.
They released 2 versions of it to allow you keep original open manager and modded open manager.