Reddit reviews Sir Gawain & Green Knight (Everyman's Library)

I'm pretty sure my copy of Gawain had Pearl and Patience in it too. I'll dig around when I get home. No wait, it's on Amazon, https://www.amazon.co.uk/Gawain-Cleanness-Patience-Everymans-Library/dp/0460875108, but very out-of-print looking.

This was my Middle English text book at university - https://www.amazon.co.uk/Book-Middle-English-J-Burrow/dp/1405117095 - along with support from https://www.amazon.co.uk/Early-Middle-English-Verse-Prose/dp/0198711018 (which also looks horribly out of print). I think you get The Owl and the Nightingale in the latter.

Not sure with any of those links whether they'll speak to your desire to follow the word into modern spelling - generally they're more interested in the meaning. But one of the details I loved while studying was watching the same word find a new definition; here's people arguing over whether beer (sorry, beor) is cider or not. http://www.tha-engliscan-gesithas.org.uk/gegaderung/index.php?topic=391.0