
Honestly I search for stories like that so often but what I found that's similar so far is:
Bloody Moon (Yuzuya)
- basically enemy princes of different nations, and one is captured..(just read it it's good )
Assassin
- seme is the king or something but the uke is a undercover spy working as his soldier.
To Take an Enemy's Heart
- I think it's the most similar, again enemies but uke has been taken a slave and his house has fallen and similar to captive prince they killed each others family. (My personal fav )

Omg I love Kouguu no Omega, ok I totally get what you mean by their vibeee, their relationship dynamic is truly the best
Then something like Smyrna and Capri have the most similar dynamic to theirs, ykow like both being confident and calm oh and them actually being enemies to lovers.
https://www.mangago.zone/read-manga/a_kiss_for_each_face/

Here's the link https://www.mangago.zone/read-manga/assassin/
No I totally understand what U mean by the western Historical aspect, I rly do enjoy BLs with those setting that I made a whole list for myself
It's giving Captive Prince