This is a projected LED red dot reticle, not an etched PRISM optic. The clarity will depend on the severity of the user's astigmatism, but projected red dot optics are usually not as clear as PRISM for users that have astigmatism of any level.
There is not a specific magnifier that is designed to accompany the SPD red dot, but NcSTAR does make a 3x flip magnifier that sits at the same 1.5" optical centerline as the SPD.
https://www.opticsplanet.com/ncstar-3x-magnifier-w-flip-to-side-qr-mount.html
This should also work with other 3rd party magnifiers that have the same 1.5" optical centerline, or absolute co-witness height.
The VISM SPD Solar Combat Red Dot Reflex Optic is backed by the VISM Limited Lifetime Warranty.
https://www.ncstar.com/support/americas-best-warranty/
There is not a way to manually turn the red dot reticle Off under the solar power mode. You may cover the solar cells with tape, to not have the red dot reticle turn On under solar power mode.
For Battery power mode, press and HOLD the Up Arrow button to turn the red dot reticle On. Tap both the Up & Down Arrow buttons at the same time to turn the red dot reticle Off from the battery power mode.
It does not. This is a red dot color with 5 brightness settings.