Should I start playing jp?

My opinion: No

You'll miss 2 years of content compared to NA and I don't think game would be fun when you don't know japanese

It depends on what you want to do, I play jp for fun and I try my luck in the gacha, but my time and focus is NA.

Until they implement a feature that just let you have all the welfares that already had their second rerun I don't think it is very worthy.
The free servants they give in this game are generally good and help a lot f2ps, so unless you plan to whale you will be at disadvantage since awesome wlefares like Chloe, Kintoki, shiki, BB etc already had their second rerun.

Why don't? If you enjoy the game go ahead.

I have noticed on my jp account that I get a ton more sq, but that's about the only pro to making a new account. It was annoying trying to navigate through all the different features on the jp version, and the language barrier in general is not too fun. Now I just use that account to roll if feel like it. So I would say try it out if you want to but focus more on NA