can you use a rail pass and get specific reservations for each train trip
DB (German Railways) has a page on the GRP with FAQ's...
https://www.bahn.com/en/offers/passes/german-rail-pass
The FAQ about seat reservations offers this link if you decide you want to reserve:
https://www.bahn.com/en/offers/Seat-reservation-and-other
If you know your itinerary, it would be wise to present it on the forum for feedback from others... GRPs are sometimes a good choice if your itinerary calls for one, but many itineraries can be carried out less expensively without a full-fledged GRP.