I'm well aware of the factors. I'm saying, given an equal platform, the Japanese rounds will recoil less than the other 'full powered' rifle rounds of WW2.Recoil isn't just about bullet weights and energy. And some of the reported energy and bullet weights are suspect as some of those original military loads are far different than hunting and/or lawyer loads of today, especially ones like .30-06 or 7.92 Mauser. You said that the Type 99 should have less recoil than a SVT-40 or G-41, but those latter two are semi auto. The gas system takes a lot of the recoil energy away from the shooter, whereas in a bolt action all of the energy goes into the shooter. The weight of the weapon also has an effect on recoil. A heavier gun will soak up more recoil than a lighter gun.
And seeing as the Type99 LMG is both fairly weighty(23lbs), and has a gas operated action like the semi autos, it's fair to say that recoil will be lower than that of the SVT-40/AVT, and G43 and fairly mild in general.