Options are in player screen and settings icon.
There you can turn on skip silence and change playback speed. There is also a mono option but available only if you choose Sonic player which is no longer supported. (You may have bugs using it so I really don’t recommend to use it)
For variable speed you can also tap the speed icon next to rewind button. It would allow you to change speed. To choose which speed to use you have to long tap and it will open a dialog. (This dialog is also accessible from apps settings and playback settings)
Finally it is also possible to define which speed a podcast should use by default when playing an episode. To do it you have to go to podcast screen (the one which lists episodes) and go to podcast specific settings.