Sodeep, thanks for sharing your experience
Definitely Bavaria-Bohemia ticket is the best option in case a group or a family travels together, such ticket almost always can beat any special offer.
The Bayern-Bohemia ticket was bought (group ticket for up to 5 persons) was bought at the Munich Central Station from a MVV Ticket Vending machine, which was not a challenge.
You did exactly the right thing, ticket machines in Germany are rather easy to use, while by purchasing the same ticket from the ticket counter you'll have to pay extra 2 EUR, which is not a lot, but still no need to pay more. So for anybody planning to use this or similar Lander tickets we advise buying them either from ticket machine or online, then you won't need to pay those additional 2 EUR.
ALX 355 is the only train without any change overs from Munich to Prague and lasts 6 hours
Actually, as of now, ALX/Ex 355 ("Albert Einstein") is not the only direct train. There is also almost a mirror train in the evening with app. same total travel time - ALX/Ex 357 ("Franz Kafka"), 17:02-23:00. Same thing on the route back - two direct trains per day (morning and evening).
...at Plzen we bought a group ticket from the conductor on board the train itself for Euro 19,60
Hmm... interesting. So you actually payed in EUR? Previously you could pay in EUR only at the station ticket counters, while now, apparently, you can do it on board as well. Good to know.
Also one small correction, 19,6 EUR corresponds to app. 470 CZK, which looks like the sum of three full fare adult tickets Plzen-Prague + 30 CZK for buying on board. So we afraid you actually didn't receive the group discount
Probably some misunderstanding between you and conductor, since group ticket for 3 passengers Plzen-Prague cost 296 CZK, if bought from the ticket counter, or 288 CZK, if you buy it online from CD eShop. But anyway you overpayed just around 140 CZK in total, which isn't that much, so not a big deal.