I just got done rereading Gakuen Alice and the romantic payoff in that manga between Natsume and Mikan is god tier and I was wondering if anyone has a good recommendation with a similar romance trope with a good payoff. Akatsuki no Yona is also a good example of what I'm looking for romance payoff and dynamic-wise with Yona and Hak. It doesn't have to be a shoujo manga, but it'd be preferred.

Maybe try one of these 2:
Zense coupling (Shoujo)
Relife (Not Shoujo but still really good)

If you're looking for slow burn romances I recommend:

Basara by Yumi Tamura
Tale of Felluah by Kim Yeonjoo
Skip to loafer by Takamatsu Misaki
Nodame Cantabile by Ninomiya Tomoko
Please Take Care of Me in This Life As Well by Lee Hye