Papo, I'm reading this as you are asking about what style of finder to use.
First off, you can get either a finder dedicated to one focal length, or one that has multiple focal lengths.
The dedicated ones are simple, and compact, but need to be changed when you change lenses. They come in cylindrical or bullet style, and an Albada type which can fold up.
The multi-focal ones come in three styles: turret, multi frame, and zoom.
The turret finder is like a bunch of dedicated finders in one package, and you rotate into view the one you need for whatever focal length you are using. They're kind of bulky, with not a very large eyepiece.
The multi-frame is a cross between a turret, and a zoom finder, as it usually has one optic with select-able frames to show the different FOV view for each focal length. Biggest drawback is the image stays the same size, with some models actually reducing the image size shown (by cropping) instead of just projecting frame lines. It's usually just as big as a turret finder.
A zoom finder will actually change the image size as you select your focal length. They are sometimes more compact than the turret or multi-frame finders, but because of their construction were more expensive, and continue to be because not many manufacturers made them. Nikon seems to be the one that most prefer of this type, but Tewe made an almost exact copy that costs less on average.