The typical use case for tablet is that you access your applications from a Qlik server using your browser. In this scenario the calculations are done on server side, and are not really affected by the tablet hard ware. The client renders as a webpage and will perform in line with any other similar web content being rendered.
For Qlik Sense the all graphics are rendered by the browser, this is why the object scale so well to your screen size. The rendering however requires data, so a slow network connection might have impact on the performance.
If you are running Qlik Sense Desktop locally on your tablet, I think you should consider getting a proper server license fro your product evaluation. In Qlik Sense the desktop client is not installed once you deploy your Qlik Sense environment, all the development work is done on the server through the web client.
