If you do a lot of re-arranging, you might get a "pro" (or do some homework) and install a "picture rail" around the perimeter of the room. Once installed, you can hand "stuff" from it without worrying about the walls.
For curtains: If the existing trim doesn't provide a sufficient base, extend that trim with properly installed boards which are fastened directly into the wall framing. You can paint the board the same color as the wall or finish them to match the existing trim. But you then have a good base to install curtain hardware without fear of destroying your wall.
Modern "wall board" is pretty forgiving and can often hold 20 to 40 lbs with just a plastic anchor. But OLD "old style" lath and plaster is a problem as often the lath has pulled away from the plaster. When you drill this stuff you have to be VERY careful and SLOW.