Unfortunately no to both questions. I have never visited CV. It was on my bucket list before the world got crazy, and now I have other concerns. On the surface it looks interesting; several diverse islands, great Canaries-style weather year-round (except some sandstorms in southern islands). The language situation is not that good. I've heard of good and bad experiences from travelers.
It is not a tax haven, and they only have tax treaties with Guinea-Bissau, Macau, and Portugal... There's a good summary of the tax situation at
PWC website. There's this gem though (individual taxation):
Category E: Capital gains
Capital gains earned by individual taxpayers are subject to a flat rate of 1% in the case of gains on the disposal of immovable property, intellectual property, or shareholdings. A flat rate of 20% applies in the case of gains on gambling, lottery, betting, prizes awarded in sweepstakes, or contests.