My advise is add. Incase they check online and ask for invoice. You can prove that you brought it.
There is no such thing as primary console for PSN account. All Console share the account. Setting primary for your PS4 is for online purposes. All PSN account is share between consoles so there is no need to set primary.
Setting primary account for PS4 is like setting administration rights for you computer. Only 1 user in that console can be primary. Usually the user you want to select as primary is the user with the PSN+ so that the other users also get permission to play online and play the games downloaded by the primary user. All other secondary user regardless of region or have PSN+ or not will share games that the primary user PSN+ downloads.
So for examples
User1 - PSN+ US Region
User2 - PSN(No +) HK Region
User3 - PSN+ SG Region
Setting user 1 as primary will allow user 2 and user 3 to have PSN+ games downloaded by user 1 and also online access. But user 1 cannot play any PSN+ games from user 3
Setting user 2 as primary will not allow user 2 to have access to user 1 or user 3 PSN+ games and play online. But user 1 and user 3 can still play online (because they are both PSN+ individually)and their respective PSN+ games. (User 1 does not share PSN+ games to user 3, vice versa)
Setting user 3 as primary will allow user 1 and user 2 to have PSN+ games downloaded by user 3 and also online access. But user 3 cannot play any PSN+ games from user 1
you're saying primary is per console? using this theory, people can create a shared account, and only buy a single ps+ subscription for multiple consoles?
I remembered reading otherwise from the link Rei7 shared before.