kingston hyperx fury is better, lower CL rate @ 2400mhz

Any DDR4 2400Mhz or 2666Mhz SODIMM should work, including the one you linked.

It came with 2666Mhz RAM, but it is downclocked to 2400Mhz. How do you check the clockspeed?

You can see it in task manager > performance tab > memory > speed.

Or also you can try this "command prompt" method:

https://www.winhelponline.com/blog/determin...ddr3-installed/



Also if you use hwinfo, it also confirms its running at 2400Mhz (1200 x 2):

Should be fine, ram mixing is totally fine.
As long your laptop takes ddr4 sodimm, they are pretty standard and work together with other ddr4 sodimm.

Sodimm = the small ram sticks for laptops.