i've got both the Top version the Novarossi version and yes they are good engines. i dunno about temps as i never use a gun but they run pretty strong. at least as good as a WS7II if not a little faster!
the seal on the front bearing went on mine quite quickly but thats no big problem & easily fixed
i've only used the Top so far & yes i'm happy with it!
i just fancied a change from RB but i still think RB are probably the best engines out there
the 421B & P5 are the best Novarossi engines for years