A QR code on a business card solves a simple problem: paper is small and your details are not. Point the code at a contact page, a vCard file, a portfolio, a booking link or your LinkedIn profile, and the person you just met can save everything accurately in a couple of seconds instead of typing an email off a 3.5-inch card.
Decide what the scan should accomplish before you design the card. 'Save my contact' (a vCard or contact page), 'see my work' (portfolio) and 'book a meeting' (calendar) are three different jobs and three different destinations. Pick one. If you genuinely need several, use a short link on your own domain that leads to a small landing page with those options - you can then change it later without reprinting 500 cards.
Physical constraints matter more here than anywhere else. Cards get printed small, handled, and sometimes put under a glass desk. Keep the code at least 2 cm square, keep a clear quiet zone of about four modules, use dark-on-light contrast, and avoid placing it near a fold, a rounded corner or a textured spot-UV finish. Always print one proof and scan it with a real phone before the full run.