Hi, im new in this psn ps plus

I have few questions hope someone can help. I just created a psn acc Malaysia, no psplus yet, after I read thru the posts here, seems like everyone strongly suggest to use US psn acc instead of MY acc for ps store games offer.

1. How to change from my psn to us psn? Need to delete the my acc then create us acc? Then set us acc as my primary acc for my ps4?

2. If change from my to us acc, does this affect the current game saves? I dont have any trophy yet.

3. If i start using us psn, does it mean i need to use us psplus as well?

4. I dont have psplus yet, my current game saves all stored in my ps4, lets say if i uninstall the game, will the game save also removed?

Thanks anyone can answer for me