Given their status as a Klingon protectorate and historical antipathy with the Romulans, I'd presume they would favour the Federation side of things, but with the changes in the Romulan administration there could be surprises!
Are the Remans even still a factor? We haven't heard anything about them since A Singular Destiny
. In STO, they are a major faction and have their own ships. (In Season 7, the Reman Rebellion joined forces with D'tan's Unification Movement for the New Romulus project.)