(02-16-2018, 02:52 AM)trihy Wrote: Do ini gets replaced when installing another dolphin build?
The default game INIs get replaced, yes. (Technically, they don't get replaced if you install a version that's old enough to not support game INIs, but those versions completely ignore the default game INIs, so the result is the same.)
But Mario Kart: Double Dash doesn't have anything set in its default INI (except StereoConvergence, which doesn't affect the performance), so it makes sense that you don't get a speedup in that game from going back to a build that doesn't have default game INIs.