Yes, brushes work to the grid (unless you turn it off - which is not a good idea for brush work).
Patch meshes are those things you can drag into any shape you like but start of as a 2d flat plane. One you make one, you can hit V to drag parts of them around to create smooth surfaces.
Patch meshes cannot be part of the hull of your map as they don't block vis. On the bright side if used inside your map they don't have to be aligned to the grid which means free rotation of them is fine and they will not deform.