Rail pass vs point to pint tickets fort

Definitely not a rail pass. Many trips can be done with inexpensive Laender tickets or local network tickets. They let you use local trains and buses in their district all day for one low price that get cheaper the more people are traveling together, up to 5 people.
Bacharach and Cochem are in the Rheinland-Pfalz state of Germany. Price is 26 EUR for the first person and 6 EUR for each additional person. Week days, you must travel after 9 am, anytime weekends.
Info here: https://fahrkarten.bahn.de/privatkunde/pauschalpreisbuchen/pauschalpreis_start.post?lang=en&country=GBR&redirected=1

Edit, I also see that the new 49 EUR ticket is available beginning May 1. It is good for an entire month for local trains and public transportation. Since it is a subscription, you must cancel by the end of the month or you will get charged another 49 EUR for June.
https://www.bahn.com/en/offers/regional/deutschlandticket

And any suggestions of must see places?

An important question, maybe the most important. Before pinning down your tickets/passes, it's important to determine what places you will travel to for sure, and what places you might or might not visit if time permits.

Actually, whether you stay in those towns you listed or not should also depend on how you answer that question.

The German rail pass, if it turns out that you want one, does not have to be bought in advance, and doing so offers no advantage. You can buy it at most airport rail stations once you arrive.

More info is needed here for a full response to your question... Please indicate how many are traveling together and ages if not adults, also how you will enter Germany - from another European country, the USA, OR?? Are you flying into FRA? Also what happens after those 10 days... do you fly home, move on to the Netherlands, or??? And how... train, airport? And which airport you will use in and out.