A menu code is scanned from a seated position, 30 to 50 cm away, often in low evening light. That sets the size: 3 to 4 cm wide, with a clear margin, and dark dots on a light card. Use the PDF export at 40 mm and the table tent will be exactly right. Glossy laminate causes glare; matte stock scans better.
What to link to matters more than the look. A web page that loads fast on mobile beats a PDF, which beats a photo of the menu. If you change the menu often, you will want a code you can repoint without reprinting every table: that is what lifetime editable codes are for, and for a restaurant it pays for itself the first time the menu changes.
A hundred table tents with the same code is normal. If you want to know which tables order most, a different code per table (editable ones with a counter) tells you, without any app.
Questions
PDF menu or web page?
A web page. It loads faster, fits the phone screen, and can be updated without reprinting if the code points at a stable address.
How big should a table QR code be?
3 to 4 cm wide for a table tent or a menu card, plus a clear margin. Use the PDF export for an exact size.
Can I include ordering?
Point the code at your ordering provider’s link. A frame saying "Order here" does the explaining.