No custom material supported at the moment. Custom texture overlays in development and will be available with the upcoming update.
Yes. web based generator required.
Scaling factor is not 1:1 to Unreal Engine 4 and is specific to SharpText. So Size:18 Text Render Actor won’t be the same size as Size:18 SharpText Render Actor.
This also under development for a while now. No ETA yet.
Didn’t test on mobile but I got responses from users on successful mobile and VR builds. No guarantee here, sorry.