I personally haven't used Schwab but have heard from other Americans living abroad/people who travel a lot that if they get wind that your trip isn't a trip, i.e. you're living outside the US, and permanently, they won't hesitate to close your account. That being said, the stories I've read are from people explicitly outing themselves to agents, i.e. "I live in Argentina and..." or "Can I change my address to [non-US address]."
Card vs WU really depends on the country you're sending your non-pesos from with WU since rates are highest in the US. The Canadian WU site seems to work with US issued debit cards and I'm able to send money for a flat fee of $1.99 CAD ($1.46) for debit to bank account transactions with a US to CAD markup of ~0.5%, so for me there's no reason to my cards here. That being said, it's nice to have as an alternative, i.e. if I screw up when I send some money, or need to make a purchase while waiting for WU to update their rates, etc.
As for getting "caught" I honestly doubt this is a something people have to worry about. Big Brother may always be watching, but he really wants USD, and what's the government's argument legally? MC and Visa have opted in, as a consumer you literally can't opt out of this scheme, so you're not supposed to use the cards? What's their argument to a judge going to be "Your honor, this retiree used their US debit card at Starbucks." Plus we're t-minus 12 months until a new presidency, there's a good chance we'll return to having 1 exchange rate again making the entire scheme moot.
Like almost all things dollars related, the fear mongering is directed at people who are fully en negro, pay no taxes, and want to use a Payoneer or Wise card from say Spain or Italy or the US to get the MEP rate. They're the people AFIP is interested in since people with savings abroad who are either kosher with AFIP can literally wire their USD here, in USD, and then sell it on the CCL market getting a rate even better than the MEP.
