The Former (by itself, see below) is more of a vanity, to have more zoom levels than the vanilla six ones we have.
As for the Latter: As far as I can see, the reason that the Interception transition is still kinda choppy while all other Geoscape animation/smoothness issues were fixed with the max clock speed option is that OpenXcom has no other Geoscape zoom levels besides the 6 we have access to, thus OXC awkwardly speeding through them with no in-betweens.
Can those additional zoom levels be added at least just for interception transitions, so it will look as smooth as seen in this video?:
https://www.youtube.com/watch?v=arWwFeYAfu0&feature=youtu.be&t=25m14s (It is at 25:14 just in case, and apologies since it is from TFTD, since in all UFO videos I found the game was set at high enough CPU speed that it made transitions instant, or the videos themselves were too choppy; And besides, it seems that in TFTD the transition speed is not CPU dependent)