Azula does have better physicals, but Toph is still pretty agile when needed, and can launch herself across great distances or move with earthwaves. Azula usually only uses flight to project herself over distances (the exception is Sozin's Comet), not simply float so it is of limited use against earth traps. While Toph did not fight azula in a duel, she did at least block her before, and since one trap is enough for her to win, all she needs is to block Azula long enough for an opportunity. Azula's physicals, the main way she avoids being hit, were not enough to outrun the protagonists in the day of the black sun, or to avoid tophs traps, once stopping her from attacking with a hidden throwing knife. Since toph could respond to her movement before it was finished, there is no reason it couldn't happen with firebending moves.
Even at close combat, where Azula has the advantage, Toph could use her earth armor to gain both enough protection and further physical streangh, which should be enough, as we have seen in Azula's fight against Aang in The Drill. On top of that, toph could avoid sight through a dust cloud, since she is alone here. So Toph chould win at least R1.
R2 might go to Azula since she can float more easily and since i do not think Toph ever took quite that much fire, but she came close. not only did she defeat (lesser, admittingly) comet powered firebenders, but she protected the team against bombs in the invasion. Since Toph survives the heat in a metal armor, there is no reason she will not in a more insulated rock armor, providing it can take the hit- and Azula's blasts were stopped by columbs, so there is no reason to assume otherwise.