Salvinis are pretty melow for cichlids, males get 8-10"max females are max out around 6". Slow growers but great looking fish as adults, females are better looking. Your red devil can only be sexed by venting.
Not exactly my opinion if a mellow cichlid. Although tempers vary from salvini to salvini, from my experience, they are pretty aggressive. They don't get very big, but they are pretty nippy.
looks like a male salvini to me and IME they are very aggressive, especially when breeding. they don't really get that big, but they are quite a nice fish