It is really outside of Wix# domain :)
Wix# is only responsible for authoring MSI and it cannot possibly control MSI performance at runtime. Remember Wix# is a compilation tool but not a runtime system. Effectively it has as much to do with MSI performance as VisualStudio with the performance of the application it compiled.
True, Wix# implements navigation between ManagedUI (specific case of EmbeddedUI) dialogs, but not for the hosting EmbeddedUI itself. And it seems that the navigation is not where you get you performance penalty. BTW EmbeddedUI hosting is not actually a Wix# feature but MSI/WiX one.
I would suggest that you (for the sake of experiment) build your msi file with the EmbeddedUI provided by WiX samples and see if there any performance difference. It is very easy, you just use <wix# samples>/Custom_UI/EmbeddedUI sample as the VS project.
Wix# is only responsible for authoring MSI and it cannot possibly control MSI performance at runtime. Remember Wix# is a compilation tool but not a runtime system. Effectively it has as much to do with MSI performance as VisualStudio with the performance of the application it compiled.
True, Wix# implements navigation between ManagedUI (specific case of EmbeddedUI) dialogs, but not for the hosting EmbeddedUI itself. And it seems that the navigation is not where you get you performance penalty. BTW EmbeddedUI hosting is not actually a Wix# feature but MSI/WiX one.
I would suggest that you (for the sake of experiment) build your msi file with the EmbeddedUI provided by WiX samples and see if there any performance difference. It is very easy, you just use <wix# samples>/Custom_UI/EmbeddedUI sample as the VS project.