The knocking part of that is obviously a gag, like many others are gag (the sneeze, the fart, the serious squirt, ecc...) but yes, there he used more strength than he did when he punches Garou with his normal punches, he exerts himself to attack but he knows he needs to use a very small part of his strength since he doesn't want to kill Garou. What One e Murata intended is that knocking a hole in a dimension is a gag that shows how ridicolously strong is Saitama
For their speed I would say that both Void and Blast are incredibly faster than FF and Sonic and see them as statues when they fight seriously, FF and Sonic attacks Void only when he is immobile in a positione, like when he had Blast impaled with his sword or when he was restricted on the ground