I'm starting to experiment with label expressions in Pro. I was able to create the image below using expressions to have the barcode font and normal font below in the same label.

My boss was impressed and now wants to know if I can make the callout boarder and lead-line conditional. The feature.field that feeds the blue text is a domain with T,F,G,S or B.
I'm looking for something along the lines of
IIF(feature.field = t, <CALLOUT> backgroundOutlineColor = [RGB dark green] + leaderLineColor = [RGB dark green]</CALLOUT>, [nested IIF() for feature.field= f,g,s and b]
Final clarification, I'm looking for an expression that controls the options below.

I've been told that using a popup, permanently displayed with HTML is an end around. If so, I'd like to see the documentation on doing that.