Yes you can use 3200 ram.
Psu....you need to tell the make and model.
So far I've bought a new Motherboard and a new CPU. The CPU says the supported type of RAM is DDR4-2666. Does that mean I HAVE to have DDR4-2666 or can I use a higher RAM type? Like DDR4-3200? The motherboard is compatible with DDR4-3200 but the only thing the CPU says is DDR4-2666.
Here are the parts I bought:
Motherboard: https://www.newegg.com/Product/Product.aspx?Item=N82E16813145035
CPU: https://www.newegg.com/Product/Product.aspx?Item=N82E16819117827
Also I have a GTX 1070 SC2 and will be using these parts along with my Coolermaster CPU fan and my GPU. Will a 750w PSU be enough to power all of this?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic