We're leaving for France soon and after a couple weeks, we will be driving into Spain. First stop Hondaribbia. We are fully vaxed and will have two boosters, three if it becomes available. We will bring our vaccination card (s). The SpTh requirements are a little vague for nonEU residents arriving from an EU country. I won't be able to complete the app requirements until 3 days before arrival to Spain. Even though the instructions seem to relate only to air travel, I'll complete the app requirements regardless so hopefully I'll have a QR code should anyone ask for it. Might hotels, museums or restaurants want to see the QR code? We won't have cell service, but I'll try to screen shot the QR code when we have wifi. Have I covered all my bases?
The SpTh QR code is only checked once on arrival at airports. I never had to show it outside the airport when I was back in Barcelona this April.
Agree with Carlos. Our one poster from Logroño crosses the border where you plan to cross rather frequently and has not been stopped, even during Covid. Friends of mine crossed it in June and nothing was required. Have a great trip.