Aha, the eternal hunt for interactive spaces for that pairing. I've been shipping Whitty and Carlos since forever, but honestly, the main spots have shifted a lot. Archive of Our Own is obviously the biggest archive, and the comment sections there are pretty active if the story's recent. People often reply to comments, and I've had some nice back-and-forths there about characterization choices.
That said, the real interaction sometimes happens off-site. I've found a few Discord servers dedicated to 'Friday Night Funkin' fanworks where specific channels exist for discussing certain ships, including this one. You have to dig around on Tumblr or Twitter to find invites, though. It's more about community chatting than platform features.
Wattpad can be hit or miss. The voting and inline comment features feel interactive, but I find the quality of discussion there is less... focused? More 'OMG' and heart emojis than actual critique or shared headcanons. Still, if you post your own fic there, you might get that quick feedback dopamine hit.