Is there a way to set the fallback for fonts when we define them not as a typescript but using \definefont?

\definefont[MyFont][Font.otf*MyFeatures]

Is there a default fallback one can specify?

Is simplefonts module deprecated or discouraged now?

When we define a font via typescript commands, we can specify rm, ss, tt, mm, hw and cg shapes for it.  Can we add arbitrary styles?  For example, I would use this for quotations, headings, etc.  Currently, I either have to spare ss or use \definefont for such scenarios.

Thanks,

--MHB