Well, because the Garmin was 100% fitness focused, while the Apple Watch feels much more like a smartphone, it has much more features than the Garmin.

Also, I do a lot of weightlifting and there are apps like Gymaholic that makes the Apple Watch a much better companion compared to the Garmin.

That’s the only reason why I use it to sleep. I used to have a Garmin, and compared to that, the AWU is very discomfortable to sleep with.

I would suggest taking a look at the activity monitor and see if it gives any clues of what’s causing the issues. Is the processor having some abnormal usage? High usage when idle? How much RAM do you have free? Test with the computer on idle and using the programs that are running slow.

Try closing everything and running a single program, like illustrator. Does it work fine? Is your machine maybe overheating? I believe the Air is fanless, so this can be causing it to throttle using heavy applications.

I believe that you need to do a bit more of diagnosing to try pinpointing the exact source of your issues

I would suggest taking a look at the activity monitor and see if it gives any clues of what’s causing the issues. Is the processor having some abnormal usage? High usage when idle? How much RAM do you have free? Test with the computer on idle and using the programs that are running slow.

Try closing everything and running a single program, like illustrator. Does it work fine? Is your machine maybe overheating? I believe the Air is fanless, so this can be causing it to throttle using heavy applications.

I believe that you need to do a bit more of diagnosing to try pinpointing the exact source of your issues