We use Cat's Best, which I believe is pretty similar to World's Best. But when cat just got into our household I decided to use his leftover clay litter to help cat get used to new place. Since there wasn't enough of old litter, I had to mix two. The result: worked the same way as just Cat's Best, very well clumped in a single ball, had no issues whatsoever. So mixing indeed works, the only thing I would be cautious about is ratio.I am on my second Maine Coon. The first grew to 25 pounds, the second weighs about what yours does (9 kg or 20 pounds). They definitely go through a LOT of litter. So Tidy Cats Breeze XL isn’t a clumping litter? I use World’s Best and have considered mixing it with another litter; mine IS a clumping litter, but might do well mixed with a non-clumping type. Maine Coons are the best, aren’t they?
And yes, Maines are the most magnificent creatures in the world