To the best of my knowledge it's a geographical name. The original bearers would've originated in Mantel in Bavaria. The variations are based on regional pronunciation. Mantheys with more Polish influence (married to Poles or living deeper inside Poland) tend to use J as we would use Y. I think this is the case of Urban Manthej as his wife's name is clearly Polish. More Germanic families use Ey or Ei. My family switched between both frequently and you may find the same to be true with your ancestors.
The area we're concerned with is historically a Hauland region, which is a term used to describe land set aside by a government/crown to be occupied mainly by farming migrants (in our case, our German ancestors). There were various tax incentives to encourage settlement, if memory serves. The suffix Hauland was used after the names of villages to signify their migrant affiliation or migrant governance e.g. Sanniki Hauland, Barczyzna Hauland etc.