Essentially, I'm looking to purchase a Yubi Key as I would like to limit the number of times I have to enter my password at home and at work. I also want to set up some applications which two factor authentication and sometimes do not carry my phone or other devices, but I always have my keys.

I have been looking at the differences and I cannot see/understand what differences there is, especially for the price.

For example, the YUBIKEY 4 comes it at roughly $40. Whereas the FIDO U2F Key comes it at $18.

So for what I want to do:

 - Limit re-typing password
 - Two Step factor
 - Maybe Near Field Communication

I believe that the NFC would be good if I had my phone, for example I could just press the key against it. But I have the mail app so I don't see this being a major issue.

Could I therefore buy the $18 U2F key to meet my needs?