Designing for SharePoint? [on hold]

Have any of you ever worked on a site that is going to be built on SharePoint? I am trying to confirm that I can do all my design work in Sketch and that I do not need to design within SharePoint.

It seems from what I am seeing online that is the case and it's closer to something like WordPress than it is to a SquareSpace or Wix where there's less design freedom. I'd love to confirm this though from someone who was worked with it before and also see if there are any guidelines that I'd have to follow.

Many thanks!