I own a DigiTech Trio+ guitar pedal, which as I understands it incorporates BIAB technology to create bass and drum parts based on the chords you strum into it. When using the Trio+, I pick a genre and style, and then I'm able to set the bass part to one of three intensity levels: normal (full complexity), medium (less complex), simple (most simple).

Is there a similar way in BIAB or RealTracks to take a particular style and adjust the bass part complexity? If so, how do you do that?

Yes, in some cases. BIAB does have the option with RealTracks for some instruments, including Bass, to select a simple version.

In BIAB, open the RealTracks Picker and when you select any instrument; if the Simple Option is available, you can select that box. If not, the Simple Box is grayed out.