I have a HP Notebook with a 15.6" screen and it fits perfectly. Also, the inside of the case is lined in a faux fur so it's really quite soft and allows the laptop to slide in and out easily. No worries for scratching.
The zip pocket is very spacious. It fits the laptop well and it’s not a struggle to squeeze it in to the sleeve. The zipper on the back is nice too. You can get quite a bit in the zipper pouch
Yes the wireless mouse fits and my power cord also fits. It is a roomy zip pocket, I enjoy the pocket very much. Of course you have to wrap the cord so it is not bundled up