In reply to Joedt:
For Nevis area basic bothy choice is between Lairig Leacach (higher but smaller) or Meanach, both reached along the aonachs/grey corries then day 2 either (part) reverse, or out to Fersit over the Easains (Leach better), or southwards over the eastern Mamores to Mamore lodge (Meanach).
Northern Cairngorms have more possibilities for "circular" overnight tours.