The further back you go, you will find spelling more and more variable. As time went on, then different lines tended to settle on a particular spelling, so you can have many strands of the same family who, in modern years, have differently spelt surnames.
My family spell their name Edmonds with an 'o', and until I started researching Family history I would have said that was the "right" way for "my" family, and people called Edmunds with a 'u' were not my family at all!
But as I worked back, spelling became much more fluid. Plenty of Edmunds and Edmends amongst ancestors. Several lines working forwards tended to settle with the Edmunds spelling, one line adopted Edmends right up to the present day. Going further back I saw Edmands, Edmems, Edmans, Emans, and 101 others.
There is no "right" spelling!
And even in recent years, transcription errors can easily occur. My own nephew married not that long ago, very much an Edmonds, but I see his marriage in the GRO index is recorded as Edmunds. So somewhere between him signing the register in the church and the record making the index, it got misread.
I only search for Edm* now and really take no notice of the actual spelling when a record is found.