The yellow ones should simply be lighter. Wider keycaps will tip over or cause the switch to jam if you don't press them centrally; normally this is prevented by a wire that holds both sides of the keycap at the same height, but in a rare few keyboards two light weight switches are placed side by side. The actuation point should be the same — if you can demonstrate that it is consistently lower on every yellow switch, then we need to see what's inside one of them.
I find that some switch types don't switch between open and closed instantaneously: if you press them slowly, the resistance falls off gradually. That's likely why some switches have a switching region: the total travel is divided into the off, switching and on regions. In the off region, it's guaranteed to be off (zero current), and in the on region it's guaranteed to be on (near-zero resistance) and in the switching region it's in-between. Mitsumi switches should behave this way too. Generally this switching region is fairly short in practice, but if your switches aren't in ideal condition they may not behave the same. The only way to be sure is to inspect the parts and see if they're the same design.
The white ones are definitely not deliberately tactile — the internal parts are exactly the same as the other linear switches.
