I have personally fallen in love with Mizani. I have thin 4a hair and it worked for me... Thick 4b? I don't know how it would work but many people love Mizani.
I made the switch from No-lye to Mizani Lye Mild and I could tell a big difference... The No-lye dried my hair out.. and I don't experience that with Mizani and also Mizani doesn't get my hair bone straight like the No-lye but I'm liking the waves it leaves behind. I lieft it in for 18 minutes... I only base my hair, ears, and neck-line when I relax and I didn't burn at all, not one tingle.
I could only find the big 4lb tub so I had to go on faith that it worked for me. And it did.
But you'd have to ask other thick 4b's how it worked for them but it worked great on my hair. Good Luck.