I actually have some experience keeping Heros rotkeil and kapampa gibberosa together, since at one time I was breeding them both and with all the grow-outs and fry I sometimes had individuals of both species together in secondary tanks. In fact, sevs (most types) and fronts have generally similar temperaments, which is also to say variable.
In a similar scenario, I had the resident Heros react similarly to an introduced kapampa-- both adults-- but within a few days the kapampa turned the tables. Cyphotilapia are powerful fish and surprisingly quick when they want to be. I'm a fairly acute observer of fish behavior and body language, it appeared to me the sev was 'offended' by the fronts bold bars. Then, after the kapampa felt more comfortable, he asserted his strength. In any case, for a time those two were going to be stuck with each other- I solved it by adding a divider, gave them time to get used to each other's presence and in time they were fine without the divider and paid little attention to each other.
Now, this was circumstantial, necessity the mother of invention and all; I'm not recommending the combination, I'm generally fussier about fish that do or don't "belong" together-- although years ago I was less so, so I've seen or done some 'odd' combinations I wouldn't do now, sometimes including Heros sp., considering I've kept them for 25 years, . These days I'd much prefer either a Heros/SA tank OR a Cyphotilapia/Tanganyikan tank, so if was me I'd go either in one direction or the other. Nevertheless, I'm saying it can be done-- that is if you keep moderate water conditions, not very low or very high pH, too cool or too warm temperatures, etc. I knew someone once who's Kigoma front and green severum were buddies in the tank. However, like most cichlids, it depends on the individual fish or tank.