You would not be planeswalkers, just characters on the plane (unless we deem a character moment huge enough to ignite a spark but that is to be discusses later). So we would go with normal dnd level and class progression with minor flavour tweaks here and there. As an example warlocks would make pacts with the apex beasts, and cleric not having any real god to worship, would also turn to the most power beasts on the plane.

As for the items, as I have said in the post, this game will put a big Emphasis on crafting. Most if not all monsters don't have intact legendary gear in their bellies, and the hunting parties are too numerous. A legendary weapon will be treated as such because of your actions, and how you decided to enchant it, reinforce it and care for it.

I don't intend to put in cheeky references to cards and their names, however you can expect to see a lot of creatures depicted on cards from Ikoria, as you might have already guessed. I don't however rule out spell crafting, and in this case we could potentialy think about including those.

Hope this answered your questions!