any stories where the bl part is just a subplot? like a story that focuses more on the cha...

I only know these https://www.mangago.zone/home/mangalist/2814594/?filter=&page=1. The BL is not exactly a subplot but the plot is interesting and more important than the romance itself

Adding to the list! I wouldn't say the BL is a subplot (maybe except in the last one), but the romance isn't the main focus of the story ^^

Checkmate
Half of Me
Honbul: Flame of the Soul
The Art of Taming the Tiger

https://www.mangago.zone/read-manga/two_way_trial_youth/

I also just remembered:

The Summer Hikaru Died
Night Beyond the Tricornered Window
Shimanami Tasogare
Smells Like Green Spirit