I actually have a hard time getting into dom/sub universe work unless the Dom is the uke, so far I can only find https://www.mangago.me/read-manga/good_work_watase_san/ (in which the dom later becomes a switch) and chapter 2 of https://www.mangago.me/read-manga/dom_sub_universe_bl/
Any recommendations?
Maybe this one?
https://www.mangago.me/read-manga/minmotion_syndrome/
Of what I know there aren't other subverses with those specifics in mangago ╥﹏╥
If you want more dom/subverses works here is a list https://www.mangago.me/home/mangalist/1738454/
The only title I can think of off the top of my head is "Metropolitan Nepenthes".
Seke partially counts, partially.
You’re right, I think it’s quite rare! I could only think of these two examples, second couple in both stories:
https://www.mangago.me/read-manga/wolf_in_the_house/
https://www.mangago.me/read-manga/color_collection/
I just remembered At the End of Death also counts https://www.mangago.me/read-manga/at_the_end_of_death/

Any BL recommendations where uke has the bigger dick compared to the seme? Just finished Biscuit and I'm craving more.
Also bonus points if Uke is taller and has a larger build as well.
Well this is 99% smut, if that's okay then: https://www.mangago.me/read-manga/shinai_to_derarenai_1/
Oh shit wait, this rec is specifically for the first two chapters, the rest of it features a different couple with only a dash of these guys.
My current obsession: https://www.mangago.me/read-manga/a_millennium_in_love_s_purgatory_offical/
black or white. they compare sizes later on and the bottom wins. it's not super obvious tho
not sure about the d* size but incase you're shorter seme x taller uke https://www.mangago.me/home/mangalist/2977817/