I lean mild Ricardian; Richard seems to have been an effective administrator and, while he certainly was a Plantagent power politician, he was certainly subjected to a lot of Tudor propaganda that tried to pin pretty much every murder in 14th century England on him.
As for whether GRRM is a Ricardian, it’s kind of complicated. On the one hand, Tyrion is depicted very sympathetically, but as someone who is hated because of his disability (and for a long time, Ricardians argued his disabilities were a Tudor invention, which turned out to be only semi-true). On the other hand, while the play in “Mercy” depicts a Shakespearean propaganda play, Tyrion did do some of the stuff he’s blamed for.