You'll get more results posting this in the effects forum.
But, imo the BDDI is a great pedal, both as a DI & FX (overdrive).
I think it sounds best going straight into yr amp rather than the fx loop.
Just bear in mind that it is a pre amp too, so in effect, you'll be using 3 pre's, yr bass, the BDDI & the one in ur amp. No matter tho, if it sounds good........
BDDI's work as a straight DI when turned off but iirc the tube emulation is still active-someone please correct me here if I'm wrong.
I like them as overdrive fx too, more than the Boss ODB-3, but the Bass Big Muff is a more FUZZ fx for sure.
Welcome to TB too