Darrenuk36
Relax, you’ll always get to travel. Always seated.
See also this blog article.
Reservations are not even possible on your listed trips within the Bernese Oberland, only on IC or EC connections between Basel or Interlaken. Have you already checked the expected occupancy rates for your travel dates, those three human symbols?
As long as only ⅓ or ⅔ symbols are highlighted for a specific connection, a seat reservation is simply a waste of money. And even in case a connection should be labeled with 3/3 human symbols in red (= high occupancy), you’d usually still find some free seats at least in the last coaches at some end of the train.