Fits all of your criteria https://www.mangago.me/read-manga/day_off/
https://www.mangago.me/read-manga/snow_fairy/
https://www.mangago.me/read-manga/ero_yume_aquarium/
https://www.mangago.me/read-manga/tonari_no_ren_kun_wa_chotto_kowai/
https://www.mangago.me/read-manga/instructor_chiba_isn_t_flattered/
The misunderstanding is cute and not drawn out. It’s my favorite so included it https://www.mangago.me/read-manga/hatsukoi_note/
Shounen Ai: Fluffville
https://www.mangago.me/home/mangalist/2536358/
Yaoi: Fluffville
https://www.mangago.me/home/mangalist/2526492/

Do y'all know any BLs that are 100% cute romance with ZERO (or almost) angst, misunderstandings, frustrating breakups, annoying third parties and such APART FROM Our Sunny Days? Just the main couple getting together and being adorable?
Because I do know a few such stories but I could probably count them on one hand