I think she could have continued to act, because they were able, if they wanted, to have a 'duties free' (or at least duties-lite) first few years, which could have included continuing to act, but Suits had ended, and who knows weather (and when) she would secure something suitable. And of course she did the Disney voiceover before they left for Canada (though released later) so there clearly wasn't a ban.
We know they wanted DC, and if they were anticipating pregnancy, that would have made a difference to what sort of work profile was realistic.
Yes, as working royals, their causes are vetted and their speeches are checked but as the royals' portfolios already include subjects such as FGM, rape as tool of war, VAWG, domestic violence - all they have to do is avoid subjects that are considered too political and too partisan in UK. It doesn't mean soft and fluffy only.