Yes, you can use only one hd spritesheet for all resolutions and you might want to turn on mipmapping to get better quality when sprites are scalled down. However you may notice that this will work a little slower than using different spritesheets prepared for target resolutions without scalling so it might not be the best approach if you need more FPS.
If I don´t use setContenteScaleFactor, the label is correctly presented.
If I use it (with 0.5 for example), the label is incorrect, looks like the texture is scaled by 2, but presented in a smaller rectangle, so it appears clipped.