Trading =/= duping save files and sending them in exchange for another duped saves.
Screenshots, your achievements, videos, etc will be always suspicious for most of the people, because 99% of SP users aren't legit. And if you are actually one of those fair guys, you will suffer/get stressed out due this distrust. This is very subjective obviously, self-confident people will barely care about others opinion.
In fact, SP is much more harder (unless you are abusing IP/TCP games, which is extra absurd). Reasoning behind this is you actually cant wait for 5 minutes so game becomes permanent and endlessly rejoin it, till you success. Also, no TP holders, of course. So, end-game content might be extra difficult to complete in the single player.
On the other hand, MXL is very easy/cheesy/abusable on p2+ and you are not going to learn/improve playing like this. My recommendation would be playing on realm, but doing atleast 75% of content SOLO, if you are playing this mod first time.