Align and Transform Not Working
Not sure if I can articulate it properly, but here we go:
By example: I'm working with a logo and each time I drag a guide down to flush against the top of the logo, it goes just past it or just above it. It won't let me place the guide directly on top. Another example, when moving items around with arrow keys or trackpad, items won't automatically center or align with whatever I'm trying to align it to. It's like if I have an item on the X axis at 12.23 and want to align item two with it, it will align to 12 or 12.5 or 13, but no intervals in between, even with an item already on that axis point. I'm having to manually type in X and Y axis properties and it's making it really frustrating. I've been consistently updating CC and haven't had this problem until CC 2018.
Attaching videos of the multitudes of issues with align/transform
As noted in comments the problem is most probably in the enabled Align Art to Pixel Grid option, in the right top corner. The grid is disabled, but the snapping occurs. There are some changes planned to streamline this workflow, because this is very generic problem.
Can't comment on the guides, as they're generally known to be a little wonky sometimes (more later) but the other issue you have *might* be due to "align to pixel grid" being turned on: There's a little sideways U shaped icon with it's open end pointed at 3 little blocks, look up at the very top-right of the application window, close to the close X and minimize buttons (on Windows machines). If it's on, it'll mess with precise alignments. Well.. they're precise to the pixel grid anyway, but probably not precise as you intend. I leave it off personally.
More on the guides... I usually look for the highest/furthest anchor point and drag a guide to that until I see the snap cursor. That works as long as the furthest edge of the vector object actually has an anchor point, if it doesn't then you're at the mercy of Illustrator's wonky guides.