Mappers are dCS secret sauce:
Let’s wait for @AndrewS from dCS to address the Mapper question. 
Yes, clicking is normal as long as you don’t hear it passing through your speakers.
It’s the device relays (one per KHz resolution, output voltage, clock settings…) you can hear click in your Rossini.
About the Filter setting persistance, the PCM Filter setting is saved for each resolution.
So if you which to try F3 for all resolutions, you will have to set it once for each…
(Output voltage, Upsampling, DSD Filter and Mapper settings are global, hence apply once for all resolutions)