The "F" chips are basically regular chips but they basically exist because Intel wanted to alleviate its shortage of 14nm chips (regular chips)
While you might want to get one because they are cheaper and you want to save money
However, you actually are getting less. While they are basically identical to their regular counterparts, they don't have integrated graphics because Intel intends its users to pair it up with a dedicated GPU. An F chip apparently has better overclocking performance though
However, IMO, you should probably stay with a regular version because the price of F chips will probably decrease again. For example, quite recently Intel announced a price cut for the F chips. That means if you buy one now, you would probably pay more compared if you buy it again later.
So if you're planning on buying a CPU now, it's better to stick with a regular K instead of a KF.
Additionally, you have the advantage of integrated graphics in case something goes wrong, such as your GPU dying