Do I need PS+ to play co-op in a party on POE2 on PS5?

The reason I'm asking is because I am currently enjoying the game a lot and I'm presently on Act IV but a certain boss is in my way. and I would like to get campaign help in clearing him.

I'm currently playing Witchhunter and I'm not exactly sure how I should gear my Witchhunter for maximum DPS/survivability.

Also which skills and support skills to use I'm currently using Galvanic Shards also I know I can play the game without plus but what about the party mechanic?

I'm not sure how it is right now, but once we hit final release (1.0) and the game becomes free, it should be possible to party play (even with people online) without PS+, as there is a general rule that free games don't need PS+.

I can't say for sure that Sony will continue that policy, but that's how it's currently expected to be, AFAIK.

Honestly, you should just try to find someone who can attempt to party up with you and see if it works.