The easiest way I know of to study what each finger does in any bow hold is to lift the fingers off, one at a time, and play a few pieces while keeping each one lifted off.  A few notes or even one piece may not be enough to notice the difference.  When I made the experiment for myself, I found that in the hold I currently use (Franco-Belgian) they do all make a difference in at least some portion of the stroke or some tempo and etc. 

At least for me, I feel they make a difference and have a job to do.  I can't say if that will definitely be true for you, though, since we don't have the same hands and etc.

There are also other bow holds.  Russian is about the only one I ever found enough info and playing examples of to try.  Didn't work out better for me than the Franco-Belgian most folks use.  I found I tended to tense my wrist too much with a Russian hold.  I also have *heard* of a German hold, but haven't actually ever found enough info on it to try it. 

I think that anything that you hear of or think of is at least worth a try to see if it maybe works better for you.  Heck, a lot of teachers have students begin with holding the bow with the thumb under the frog.  For some children or adult beginners, it can be a less awkward way to hold at first while the hand develops strength and dexterity.  It does not seem to hurt their later development at all, from what I hear. 

The pinky finger, some people just don't use much in everyday life.  Our world is set up to be able to dodge around using it most of the time.  But it *can* be very useful, once it has had enough practice and work to be a "productive member of the team".  A non-violin example most of us here are familiar with is typing.  Some type with just their first fingers, some use maybe the first two fingers and thumb, etc.  Touch typists who have practised using all the fingers of both hands can usually type considerably faster and surer, though.

With violin, the pinky floating up off the bow is very common, especially early on.  Enough so that there are exercises and assorted gadgets to train the pinky to rest in a particular place on the bow.  So you definitely have a lot of company.  My bow hand pinky used to "levitate" quite often, and eventually I used a home-made version of a gadget called a "pinky nest" for about a month to fix that. 

Anyway, experiment, try different things, and if something seems to work for you at least right now.. go with it.  But I suggest you keep experimenting at least every now and then, especially when you run into pieces that are being a challenge.  Maybe at some point you will find places where you want that pinky doing a job.

And maybe not.  I recall reading that some of the old masters kept the pinky definitely lifted off the bow, and they obviously could still play well.  But I don't know enough details on that.  They may have been holding it a little different, their bow might have been balanced a little differently, there may have been some trick to it.  Or maybe a lot of years of many hours of practice. 

But I personally don't believe that there is some one perfect way of doing things that is just always best for everyone.  We all have different hands, wrists, arms, fingers, etc.  Explore, experiment, learn, use.