If you use a normal unity orthographic camera, where orthographic size is 10 - creating a sprite collection with explicit ortho size 10, height of 768 will give you sprites which are pixel perfect at that resolution.
If you create a tk2dCamera with 100 pixels per meter, then creating a sprite collection with 100 pixels per meter will create sprites which are pixel perfect at the native resolution of the tk2dCamera.
One nice thing of using pixels per meter, is at 100 ppm, moving objects in pixel increments is easy - just make sure the number is perfectly divisible by 100 and you're good to go. Eg. 1 pixel increment is 0.01 units. Its not the case with an ortho camera.