In the modern Western world we may experience some people hyphenating their names upon marriage. But apart from some celebrities adopting entirely new surnames as they enter the public sphere, our most common experience is that males have the same surname from birth to death, and females may change their surname only upon marriage.
History is messier.
Anyone who has been doing genealogical research for any significant length of time has discovered that surnames are complicated things. A person may be born with one surname and in later life adopt a new one, or at the very least a new spelling. Or they may have no consistent spelling of whatever surname they use (sometimes to blame on their illiteracy and sometimes to blame on the recorder's unfamiliarity with the surname). And, of course, there are surnames altered by immigrants as an attempt to fit in with their adopted country and to improve their chances of employment in a country that may otherwise treat non-natives from some areas of the world as being less desirable for hiring and doing business with. There are also stories of individuals adopting surname changes in order to avoid legal problems or to disassociate themselves from relatives who they are at odds with.
And we must deal with all of this as we label our digital files and folders, as part of our genealogical research. What spelling do we consistently adopt for a surname that may have spelling variations in the records? What name do we file documents under for an individual who may have changed their surname over time? (I don't have time in this posting to address the first name issue. That will have to wait for another posting.) The spelling variation that occurs only in a small percentage of records, in my opinion, can be essentially ignored, at least for purposes of creating the surname folder.
Three of my grandparents' surnames are extremely common, and as a result, are not as likely to result in spelling errors or variations: Smith, Martin, and King. While I may find different spellings for those surnames hundreds of years ago, I'm not there yet. But my 4th grandparent (Weinglass), and the remaining great-grandparents (Bannon, Bodie, Foshee, and Grodovitz) present interesting problems.
The Bodie family of South Carolina is descended from the Boddie family of North Carolina and Virginia, and even some of the South Carolina family use the Boddie spelling. The branch that left for Louisiana also spells it Boddie, and some of my direct ancestors can be found using both spellings. Because both spellings are very common, I plan to use Bodie/Boddie (while the order isn't all that important, my more immediate ancestors use the Bodie spelling) to identify that family.
Bannon is similar to Bodie in some ways, in that more recent records seem to have standardized on Bannon, while earlier records frequently have Bonnon. I plan to start by using Bannon, but I may switch to Bannon/Bonnon if I discover a large number of records with the other spelling.
Weinglass appears in a variety of spellings in the records (Weinglas, Wineglass, etc.), but all of my most recent relatives have standardized the spelling as Weinglass, so I expect to use that one for the surname folder.
Foshee is trickier. Lots of different spellings for people who are probably related to each other. Because my most recent relatives seem to have standardized on Foshee, I'll stay with that one, to keep it simple.
I have very few records for Grodovitz so far, so I will probably adopt one spelling for now, with the idea that I may need to change it if I find that another spelling is more common in the records.
My major point in this posting is that there is no hard-and-fast rule as to how to create surname folders for surnames that may appear different ways in the records, and you'll have to consider a number of factors before deciding which spelling to use and whether or not to use multiple forms of the surname. Whenever possible, keep it simple, but don't get hung up on doing it "right" the first time. It's ok to change your mind later.