Reddit reviews Le Morte D'Arthur: Volume 1 (The Penguin English Library)

I'm far from a medievalist, so take my suggestions with a grain of salt.

One approach you can use is to pick up the Norton Critical edition of Malory's Morte D'Arthur. Norton Criticals are great because they gloss vocab well plus they include relevant essays that can be great for providing some extra perspective on a piece. All in one package, nice and easy. Then again, they're not exactly light reading. For slightly lighter reading, there's always Penguin Classics editions of similar writing (linked is Malory, but there's also a Penguin Classics of Chretien de Troyes' Arthurian Romances). Penguin editions will edit the text for readability without sacrificing too much - but you're likely to see modernized spellings (for most people, this is a good thing). On the other hand, Penguin classics won't include criticism inside the book, save for the introduction. A final option is Oxford World Classics, again, of Morte D'arthur. OWC are one of my favorite to teach from but they have an annoying footnoting system that can take a little bit to get used to, at least in my opinion. OWC books are generally edited very well, though, and you'd be getting a good experience of the ur-text of Arthurian legend. But again, likely to be pretty darn heavy.

As for Gawain, I read it in college and then haven't touched it since. Sorry I can't offer any interesting studies on it.