Settings and customization after upgrade?

Hi there,

I'm still relatively new to the Mac experience and this would be my first OS upgrade on a Mac going from Mavericks to Yosemite.

My concern is that I have customized a bunch of things, such as how the mouse moves, deactivated all gestures, location of the iTunes database, some settings for my photo software, drivers for my audio hardware and Logic, a few scripts that speed up workflows or replace options not native to Macs, stuff like that.

Will this all carry over during an upgrade? Or do I have to go in and make all those tweaks again? And if stuff doesn't work how difficult is it to go back for instance via time machine and re-install everything the way it is now?