My family and I will be traveling from Venice to Berlin via rail in mid-February. We would like to take our time and stay overnight in a few places along the way (Bolzano, Innsbruck, Munich, Leipzig). Is this possible with a single purchase of a Venice to Berlin ticket for each of us? Is there a pass that would serve us better? Thanks!
Neither.
You can't use a ticket and stop stop along the way for various overnight stays.
A pass is very unlikely to make financial sense in your case.
You may purchase tickets for each sector. In advance if you want to save, on site if you don't care about money spent.
"You can't use a ticket and stop stop along the way for various overnight stays."
Not exactly true, but your request is difficult.
The problem with booking your route online from the Bahn is that, for the most part, the Bahn does not book online segments completely outside Germany (ie, Venice to Bolzano). You could book that part separately from Italian Rail or ask the Bahn for a price request for the entire route.
However, I was able to find an online price for Bolzano to Leipzig with 48 hour stopovers in Innsbruck and in Munich. I was even able to get discounted advance purchase tickets for this route. Two stopovers of 48 hours each (Innsbruck and Munich) is the maximum.
Use the German Rail query page to explore other options.
How long do you want to stop over in Bolzano and Innsbruck? If you can limit those stopovers to 48 hours each, you can get an online ticket from the Bahn, either full fare or Savings Fare, from Venice to Munich, with 48 hour stopovers in both Bolzano and Innsbruck. Then you could stay as long as you wanted in Munich and use another ticket to Berlin with a 48 hour stopover in Leipzig. If you spring for the full fare ticket, I think you can use any train, i.e. leave earlier (but probably not stay longer than 48 hours).
Full fare tickets are "fully flexible", that is, you can commence the trip anytime within, I think, a month of first date of validity on the ticket, but once started, you have to finish the trip within some time limit.
For a normal ticket, ie, one without stopovers built in, I think you have to finish the trip by the end of the second day after starting. You can stop as many times as you want as long as you finish in time. (For trips shorter than 100 km, I believe it is the end of the first day.)