I have 2 profiles on the same ps4 machine a us and a uk one while I am aware that dlc is region locked, can I get one psn plus subscription and all regions will play online multiplayer? And is it better to keep the uk or the us as primary? I see the us are cheaper Thank you
Your PSN Plus subscription and its benefits are only relevant to the account it is associated with. Any other account will only benefit from the subscription in that you can play the games licensed to the device. Online multi-player that requires a Plus membership is not accessible to the other accounts.
Technically, it's not what account is primary for the device. It's more a case of which device is primary to the account.
Personally, if you have a choice between the two, I'd say look at which one has the best free download offerings and go with that one. You can always subscribe to both as well.