I'm glad I didn't know about not mixing cabs. Done it all my life. Well, all my bass life any way.
The sound when I use a TE cab loaded with an Epifani 10" paired with a TCE 2X8 is orgasmic.
Similarly 12" BF with a 15" BF.
15" Bugera in a TE box paired with a TE 2X10 also sounds amazing.
Suck it and see is always my advice. What you hear, what you like is the only thing that matters. Remember unless there's a bassist in the audience no one but you really cares.