While not a complete list by any means, these are some unfamiliar name variants I could think of off the top of my head.

Generally, all forms of Arthur are too close to the original to fool anyone. The best I can think of is [**Artair**][1], the Scottish form.
Though you could use a Welsh/Old Brythonic name like [**Arthmael**][2] ("bear prince").

Morgana/Morgan le Fay is similarly difficult to obscure, since her earliest name is still [**Morgen**][3].

Guinevere has many variants. Some of the more unfamiliar ones may be [**Guanhumara**][4] (Geoffrey of Monmouth's rendering in Latin), [**Wenneuereia**][5] (used by Gerald of Wales), and [**Findabair**][6] (the Irish cognate). [**Winlogee**][7] is presumably Guinevere in a carving on the archivolt of Modena Cathedral in Italy.

For Gawain, there's [**Gwalchmei**][8] (Welsh), [**Gualguanus**][9] (Geoffrey of Monmouth's rendering in Latin), and [**Gauvain**][10] (French). [**Balbhuaidh**][11] is the Irish form.

[**Arnive**][12] was the name of Arthur's mother in [Wolfram von Eschenbach's *Parzival*][13].

[**Bedwyr**][14] is Bedivere's original Welsh name. [**Beduerus**][15] is Geoffrey of Monmouth's rendering in Latin.

[**Galath**][16] and [**Lanslod**][17] for Galahad and Lancelot.

[**Medraut**][18] is one of [many variants][19] of Mordred. It's also the original.

[**Myrddin**][20] is the Welsh name for Merlin. 

In place of Camelot, there is a pretty decent list of courts Arthur had, in Welsh sources: [**Caerleon**][21] (his capital [according to Geoffrey on Monmouth][22]), [**Mynyw**][23], [**Pen Rhionydd**][24], and [**Celliwig**][25]/[**Gelliwic**][26].


  [1]: https://www.behindthename.com/name/artair
  [2]: https://www.behindthename.com/name/armel
  [3]: https://www.behindthename.com/name/morgan-2
  [4]: https://forvo.com/tag/guinevere/
  [5]: https://en.wikipedia.org/wiki/Guinevere#Name
  [6]: https://en.wikipedia.org/wiki/Findabair
  [7]: https://en.wikipedia.org/wiki/Maleagant
  [8]: https://forvo.com/word/gwalchmei/
  [9]: https://forvo.com/word/gualguanus/
  [10]: https://forvo.com/word/gauvain/
  [11]: https://forvo.com/word/balbhuaidh/
  [12]: https://forvo.com/word/arnive/
  [13]: https://en.wikipedia.org/wiki/Igraine
  [14]: https://forvo.com/word/bedwyr/#cy
  [15]: https://forvo.com/word/beduerus/
  [16]: http://www.maryjones.us/ctexts/triads4.html
  [17]: https://forvo.com/word/lanslod_lak/
  [18]: https://d.lib.rochester.edu/camelot/text/arthurian-references-in-annales-cambriae
  [19]: https://forvo.com/tag/mordred/
  [20]: https://forvo.com/search/Myrddin/
  [21]: https://forvo.com/word/caerleon/
  [22]: https://en.wikipedia.org/wiki/Caerleon#Arthurian_legend
  [23]: https://forvo.com/word/mynyw/
  [24]: https://forvo.com/word/pen_rhionydd/
  [25]: https://forvo.com/word/celliwig/
  [26]: https://forvo.com/word/gelliwic/