You can use either, but I’d suggest using bindToDrawFrameofSize. It uses an internal FBO, which means you will need to get the captured frame from the Syphon Server, in your server app, and draw it on a quad in your NSOpenGLView to see it there.
To fix the size / clipping issues, ensure your passed in sizes match the viewport, size of your NSOpenGLView, etc, and that your ortho and coordinate system assumptions are correct.