I'm a worrier also - no need to apologize.
Hint - being a worrier, I double check the departure time of my scheduled train the night before and prior to heading to the station on day of the journey. Not Spain, but this paid off last summer when my departure station in Hamburg, Germany was changed. I didn't receive a text or email despite having purchased through an account attached to my phone and email with the rail carrier. I was lucky I had checked. The new station was not close to the original on the ticket.
Spain specific - I purchased Renfe tickets via my Renfe account about 2 months in advance for an upcoming trip. I have received emails that one of the arrival times has changed slightly. I will still follow my standard operating procedure and continue to verify the specifics of my booked journeys. I would hope to be notified of changes, but am not risking missing a message.
Renfe does not use the term "First Class". It calls that service "Elige Confort". After selecting the ticket under the "1st Class" banner on Trainline, it will display those words on the "Selected Journey" detail.
Renfe's fare and ticket levels and terminology are not intuitive to many. Scroll down here to Scudder's explanation https://community.ricksteves.com/travel-forum/spain/sevilla-to-barcelona-ave#:~:text=%27Elige%20Standard%27%20will%20be%20in,access%20and%20food%20service%20included.&text=*Only%202nd%20class%20seating%20offers%20a%20formal%20Quiet%20Car.
For what it is worth, I have had very good experiences purchasing Renfe tickets directly from their website for multiple trips with a US Visa and MC. I use the app to store my tickets and easily transfer them to Apple Wallet on my phone.