Input lag on new build

[Ruler1976]

So I just built a new home office pc for my mother and its having some serious input lag on the mouse even in bios.

The parts are.

AsRock B250m-hdv

i3-7100

Crucial ddr4 2x4gb 2400

Evga 400w PSU

Samsung evo 850 500gb ssd

windows 10 legit copy lol

Lite-on DVD-R she has tons of picture cds to convert lol

I have contacted AsRock and am waiting on an RMA for my MOBO they jumpeds on the RMA without ANY troubleshooting just my word so its either a known issue or a lazy rep.

But I'm a little worried about memory compatibility the brand size and speed are on the mobo list but its a different sku. Does that matter?