If we get down to the math and physics of it, 8mm out of 630mm is about 1.3% linearly, which should approximate the difference in ride quality due to road surface. And it's about 2.5%, when taken to the second power, which should approximate the difference in lateral agility and longitudinal acceleration. The foregoing is speaking for the contribution of the components at the periphery of the wheel only, i.e, rim, tube, tire, tape, and spoke nipples. Obviously, changing the wheel diameter does not affect the contribution of the rest of the bike to ride quality, lateral agility, or longitudinal acceleration, everything else being held equal. So the net contribution of an 8mm change in rim diameter must be somewhat less than 1.3% to ride quality; and somewhat less than 2.5% to lateral agility and longitudinal acceleration.
If the net mass of the rim/tube/tire combination changes significantly when comparing 630 to 622, then all bets are off.