As far as I know arcgis wont let you use diferent transparency setting for fill and border.
One workaround is to duplicate your layer and set the bottom one with no border and the top one with only border and no fill, then you can style your fill and border to your liking. Of course this work only for polygon layer, for text box it will be harder to set it ...
The Description is a html content. You can set the style for the descriptions.
<div style='font-family:JetBrains Mono;font-size=20;font-style: italic;'>Input GPS CSV file with X,Y fields and output the feature class.</div>