1) You need to detect the platform requesting the layout:
Set Variable $$appVer =
PatternCount ( Get ( ApplicationVersion ) ; "Pro" ) = 1 ; "Pro" ;
PatternCount ( Get ( ApplicationVersion ) ; "Web" ) = 1 ; "Web" ;
PatternCount ( Get ( ApplicationVersion ) ; "iPad" ) = 1 ; "iPad" ; "Phn")
then based on the variable above pick the layout with the "layout name by calculation" and use the case statement below:
Go to layout [Case ( $$appVer="Pro" ; "layoutPro" ; $$appVer="iPad" ; "layoutiPad" ; $$appVer="Web" ; "layoutWeb" ; "layoutPro" )]
you need to make sure the Web layout has the classic theme the other layouts can be your choice.
Hope this helps,
in fact I think it´s a shame that IWP can´t use any of the new themes. This is a major step back for IWP. Same already happened with script triggers. Hopefully this is no sign for the end of IWP at all.
Thank you very much for your answer. It helps.