Lowkey forget if there are misunderstandings but here:
https://www.mangago.me/read-manga/behind_the_desk/
https://www.mangago.me/read-manga/bl_motel/
https://www.mangago.me/read-manga/no_love_zone/
https://www.mangago.me/read-manga/unriped_expression/
https://www.mangago.me/read-manga/tractor_full_of_love/
Wouldn’t qualify as fluff, but if I’m remembering correctly it’s still sweet:
https://www.mangago.me/read-manga/his_house/
Unfortunately does have some misunderstanding, but fit all other criteria:
https://www.mangago.me/read-manga/honey_bear/
https://www.mangago.me/read-manga/the_third_ending/

BL + fluff + 60 or more chapters + completed + full colour + no/little misunderstandings + unique plot + not historical + not fantasy. Please!! Thank you