Reservations and the Railplanner app, which is yout ticket, are separate so there will be no link between your reservations and the app.

Passes and reservations Mandatory and optional) are separate entities and rarely, if ever, do they specifically link to a pass, but routinely show at least the lead passenger name. As long as the reservation is for the correct train, irrespective of how you sourced it, and the correct name where included you simply show your validated pass (QR code and train listed) AND the confirmation for compulsory reservations  (pdf or paper as required) you are fine. 

Some reservations require proof of a pass to make the booking (e.g. Eurostar or the Eurail service) but this is not shown on your reservation in case you have to exchange your pass before travel.

Thanks, I feel better now.

I just made my reservation but did not get to make seat choices. Is that not possible with 2nd class tickets? We’re traveling from Paris to Zermatt. 

The Eurail reservation service does not offer any seat choice. Depending on the train, you can sometimes choose your seat when you book elsewhere.