Point Size with DX11

To use pointsize with DX11 mode, you need to use DX11 billboard shader:

Here is image with default point mesh shader (only works in DX9 mode)

And here with DX11 shader (supports "size" by billboarding each point)

Where to get those DX11 Quad/Tri shaders?

DX11 point size shaders can be currently accessed through PointCloudTools/Materials/Shaders/Extras/
Clicking the link inside that folders open page where you can download the shaders (save them to your project and assign into DX11 viewer material)