Question about German surname variants

Hey! I was wondering if anyone here had some more information about German surname variants. Specifically, how they developed multiple spellings. My surname is Niedermeyer, but I’ve also seen it spelt Niedermayer, Niedermayr, Niedermeier, Niedermaier, Niedermair, Niedermeijer, etc.

When I was doing research, I saw it could be due to regional dialects and migration, but I was curious what this means. Why would someone change the spelling from -meyer to -maier and so on? Do we know what regions changed their spellings to what? Is there anything about the variant that we can use to tell us something about someones migration history? Or how to find the original spelling?

My family is from Hamburg and uses the Niedermeyer variant. I’ve been told that our family has lived in Hamburg since the begging of time (lol). But when I tried looking up notable people with our way of spelling, it didn’t bring up much and the Meyer variant in general seems to be all over. Some spelling like -meijer seem to be undoubtedly Dutch, but other than that it seems like a mixed bag. So is there any real Rhyme or reason why spelling changes?