Strasbourg to Basel to Munich

There is a similar pass to the Bayern-Ticket for Baden-Wuerttemberg. You could go from Strasbourg to Kehl with a local ticket and buy your Baden-Wuerttemberg pass there, but you might wait a while for the next train. Better to buy a ticket all the way to Offenburg. There are a lot more trains stopping there. Once in Baden-Wuerttemberg (Offenburg), take an RE up the river to Basel Bad Bhf. This Bahnhof is physically in Basel, Switzerland, but was built by German Rail and is considered a border Bahnhof for the Bahn, and included in the B-W Ticket. From there, anywhere in Basel is an innerzone ticket for 2-3 CHF. When you leave Basel, go back to Basel Bad Bhf and use the B-W ticket to go along the Rhein to Singen. You'll go through Schaffhausen, Switzerland, but that is covered by the B-W ticket. From Sigen, you can go along the No. bank of the Bodensee to Lindau with the B-W ticket, and, of course, you can use a Bayern-Ticket from Lindau to Munich.

Now im contemplating just going from Frankfurt to Basel and then to Munich etc., would you recommend Heidleberg to stopover for a night on the way, to break up the journey, maybe direct from Frankfurt to Heidleberg ( do you know the cost not booking in advance?) and then getting the BW pass for the rest? Or is Heidleberg to Basel to far?

Most of these questions can be answered with the German Rail website. Without advance purchase, you'll pay standard fare. That varies with the time, train type, number of connections. From Frankfurt to Heidelberg, there are some direct IC connection that average 50 min and will cost €19/P. ICE connections will cost €26 and take longer because you'll have a train change in Mannheim. Finally, there are direct regional trains for €15,80 and 1½ hrs. Mannheim and Heidelberg are in Baden-Wuerttemberg, so you will need a point-point ticket to Heidelberg (the first day) and can use a B-W ticket to Basel (the next day). Heidelberg to Basel Bad Bhf using a B-W ticket will take just under 4 hours to just under 4½ hrs depending on the time of day. There's a connection (S-Bahn to Mannheim or Karlsruhe, one more change in Offenburg) every hour.