Max RAM allowed for HP Laptop 15-db0011dx?

I'm having a serious performance issue that started about a month ago I think? Every time my memory usage goes above 85% or so, YouTube has trouble streaming smoothly, it makes an intermittent buffering sound (repeated sound is the best way to fix it to describe it).As if the computer is trying to produce the video and sounds but is having problems with it.

I've been wanting to take advantage of these Black Friday deals to get more RAM, but I have no idea what the max RAM allowed is for my laptop model.

As a side note, this performance issue started when I noticed a change in the name of my computer which I can't remember. Shown below. Does anyone have any idea what might have happened? First I called my home computer and that name is correct doesn't match my model name 15-db0011dx. It's very strange. Thanks for any help on any of these issues.