Generally speaking, I don't think there is one particular person who is pumping out several high quality maps. Map making is still a very laborious process. The only thing you can do is peruse the Mods and download some maps. Then follow the maker of the maps you think are high quality. Or contact them if you want to collaborate/hire/whatever.
Detailed doesn't mean good maps. I know someone very famous on the BeamNG modding community who makes maps that can't be called good despite their dev-quality. (won't tell his name (edit: already done))
https://www.beamng.com/resources/authors/spencer-johnson.166517/ this dude makes some of the best maps out there --- Post updated --- makes lots of fun challenge maps but some amazing beutiful detailed citys to
his patreon is jsut wip/wip released more amazing maps --- Post updated --- maybe some exclusive ones i think to