Thanks for all the replies guys.
I've just realised that the Token
BB i have for my Sram Reds will work with the DA 7900 crank.
Sram cranksets has a tapered axle which go from 24mm on the drive side to 22mm on the non-drive side. The Token BB uses an alloy shim to make that reduction. If i don't use the alloy shim the BB will be 24mm on both side, which is what i need.
The biggest problem that i had when i used a plastic type BB on the Reds was serviceability. I found it really hard to remove without damaging it in one way or another.
If i had to buy one i would probably just go with the BB91-B just because it's cheap and may help with unwanted creaking.
Thanks to the weight of Di2 i've given up on being a true WW so no ceramic bearings for me.