Chapter: 387 (DBZ 193), P10.3, P13.1-4
Context: Goku just achieved Super Saiyan Grade III for the first time.
Gohan: “Ab-absolutely incredible power! You’ll definitely be able to defeat Cell like this!”
[ ]
Goku: “I can’t win like this…Probably not…[ ] With my muscles swelled up like this, my power greatly increases, but it kills my speed. Huge power doesn’t mean anything if I can’t hit my opponent…And it uses up energy at too intense a rate. Balance-wise, regular Super Saiyan is best. I know that well enough…”
Chapter: 391 (DBZ 197), P7.2-7
Tenshinhan: “…Hey, Goku and Gohan were Super Saiyans just now, right? But even so, they were very…how do I say this?...Natural-feeling…”
Piccolo: “…I think there’s no doubt that they were Super Saiyans…However, they’ve trained so that they can exist in that state at an ordinary, everyday level…”
Trunks: “S-so then…When they fight, they’ll [perform] an ev-even more tremendous transformation…!”
Vegeta: “Are you an idiot?...You don’t seem to think things over…They’ve judged that state as the best! If they get used to that as a matter of habit, then even if they raise their battle power, the strain on their body is very small! [ ] They’ve thought this through…”
It is regular Super Saiyan with Base-like stamina. It doesn't get more complicated than that. There are no new special abilities or powers.