Yes, local accounts are those that exist - are/have logged in - on the same console, whether created there or elsewhere.
The Playstation Plus subscription is tied to the SEN account, but that account can specify a single PS4 console as its primary PS4, which enables other (non-PS+) accounts to access everything on the console.
So any account using that console (the one specified as the primary by at least 1 PS+ subsriber) can enjoy the benefits of PS+, when using that console. That includes multiplayer.
I assume though that multiplayer is not available to local accounts if you are online and playing multiplayer on someone else's console. That part isn't exactly clear. But your (non-PS+)family members / housemates could definitely play multiplayer on your console with only your PS+ subscription when you're not using it.
This FAQ on playstation.com is fairly detailed:
PlayStation 4
You can activate one PS4™ on your Sony Entertainment Network account
(this is known as your Primary PS4) and temporarily activate a second
PS4 on your account.
PlayStation Plus benefits available to other non-subscribing users on your Primary PS4:
- Online multiplayer (subject to any parental control settings on sub-accounts)
- Play downloaded games purchased with PlayStation Plus discount
- Play downloaded IGC games
PlayStation Plus benefits not available to other users on your Primary PS4:
- Purchasing PlayStation Plus discounted products from PlayStation Store
- Online game save storage
- Auto patch download
- PlayStation Plus exclusive early access to game trials
PlayStation Plus benefits available to you on a non-subscribing friend’s PS4:
- All of your PlayStation Plus membership benefits are available to you when you use a friend’s PS4.
PlayStation Plus benefits available to your non-subscribing friend when you use their PS4:
- Play downloaded games purchased with PlayStation Plus discount
- Play downloaded IGC games
PlayStation Plus benefits not available to your non-subscribing friend when you use their PS4:
- Online multiplayer (subject to any parental control settings on sub accounts)
- Purchasing PlayStation Plus discounted products from PlayStation Store
- Online game save storage
- Auto patch download
- PlayStation Plus exclusive early access to game trials
When you sign into your Sony Entertainment Network on a friend’s PS4
the system is temporarily activated on your account. Please ensure
that you correctly sign-out of “PSN” on your friend’s system to keep
your account secure.
If your “PSN” account is inactive on your friend’s PS4, the system
will be deactivated automatically from your account and your friend
will lose access to any of your downloaded content. This content can
be deleted from their system hard drive by going to Image (Settings) >
System Storage Management > Applications. Next, highlight the game to
delete and press Options > Image (X button).
Source: http://faq.en.playstation.com/app/answers/detail/a_id/5030
At present, there is no way to transfer trophy information from one account to another (still). Logically, it doesn't make sense for trophies to be transferable. This person earned this proof that they did something - what meaning would these have if you could transfer them to someone else? This would certainly allow for a shim to act as a psn id change, but that would be the wrong solution to the problem.
Some few saves and other data can be copied over but often, like trophies, these are usually non-transferable as well. To determine which data can be transferred, you would have to go through each and try it. The logic behind this is probably the same as trophies and possibly even related to how much easier it is to cheat trophies with someone else's saves.
You still cannot change your psn id and there are no practical workarounds. All you can do is start over. Sony might have reasons, but it is a hotly discussed feature that exists on the Japanese PSN. There has never been an outright denial of the future possibility (only statements that implementing this feature is "very technically complex").
On PS4 you can sort of get around this by changing your real name, but that doesn't allow numbers or special characters and will not help you on PS3.
Best Answer
Yes, PSN accounts are different to ps4 accounts. You can use your PSN account on as many ps4 user accounts as you like. The ps4 user accounts only contain your game saves, so deleting a ps4 account will not delete the PSN account linked to it or it's subscription. And if your worried, just log onto the other ps4 account with your game saves with your PSN account, no need to delete the new one if your worried.