I'm running into this issue as well and _really_ can't play the game while the issue is present.
I've gone through basically everything I've found on line that even seems like it's related to this:
- defaults write .GlobalPreferences com.apple.mouse.scaling -1
- almost identical command that I saw somewhere but had larian in the command
- changing my mouse options in settings on my mac
- using the trackpad instead of my magic mouse 2
- using a crappy wired logitech mouse; surprisingly this did make it slightly better but still had isssues where it was strying to select things layered underneath the currently active window

Please note that it's not just trying to select items on the ground, for instance if I open the skills window in the inventory screen, I can't seem to expand any of the windows without clicking 20 or so times, since it keeps highlighting items that are being worn in the inventory screen.

This also has a HUGE impact on character creation screens as it stops the pop up explanation text from appearing over any descriptions.

System specs:
Macbook Pro (Retina 15-inch, Mid 2015), OS 10.14.5
2.2 GHz intel Core i7
16 GB 1600 MHz DDR3
Intel Iris Pro 1536 MB