Hello, long-time lurker here, I've transcribed all of Byleth (M) and Edelgard's supports. Since Byleth has dialogue options I've marked his choices with a ">" and numbered them with the response if you pick them. The conversation picks up again where "Both" is noted. There is only one conversation where the choice appears to affect character's affection levels.
Edelgard x Byleth C
Edelgard x Byleth C+
Edelgard x Byleth B (This conversation's choices seem to affect character affection)
Edelgard x Byleth A
Edelgard x Byleth S
Edit to add: I finished Hubert and Byleth (F) too.
Hubert x Byleth C
Hubert x Byleth B
Hubert x Byleth A
Hubert x Byleth S
Enjoy!