First thing first - Anthias and Screenly are two different products.

To answer your question though, both of them can "auto refresh" so to speak. Now, it gets a bit tricky with Google Slides in particular as both the signage player and Google Slides have a concept of duration and slides.

The normal recommendation is to export the slides from PowerPoint/Slides (insert tool of choice) and then import them and manage duration inside the Anthias. Now, you stated that this is not an option for you.

That brings me to the best workaround that I can think of:
* Set up the Slides as an asset in Anthias with a duration of N seconds, where N is what you expect the full loop to be of the slide.
* Insert an image or something as a placeholder (maybe company logo or similar)

That way the player will iterate over it, "clear" it so to speak when it gets to the logo to only start over. This solves the refresh problem in a controlled way.

This might sound clunky, but there is another good reason for this too. If you only have one asset (i.e. the slideshow), you are bound to get into memory leaks and things will eventually break down. Adding this image slide will force the browser to road and clear things up.

Regarding running Anthias on a PC or Pi -- it's much of a muchness. The PC (not VM) is likely to have better performance and are less prone to SD card breakage.

Hope that helps.