For example, with lighter weights (let´s say 20 or 30 kg in plates), pushing it on this machine feels much harder than pressing the same weight on classic bench press
I have a theory, see if it makes sense: under these weights on the machine our body is not yet using a lot of auxiliar muscles we often use on free weights, so the exercise is more concentrated. When huge weights come into play, that's when gravity really makes us fight hard, so the machine helps alleviating that.
Yeah, maybe. You better come over here and try for yourself :D
Leees do it! I've been hiting the gym, but more focussed to cycling and not as much to gain mass