I'll be arriving in Munich on a Thursday afternoon and will head directly to Fussen. I have tickets to tour Hohenschwangau and Neuschwanstein castles at 10am and 12pm, respectively. After I'm finished with the castles I will head back to Munich, where I'll meet up with a friend. The following morning (Saturday) we'll take a train to Salzburg.

Depending on how the timing works out, I see two possible scenarios for train tickets. Please let me know if there are any errors in my thinking.

Option 1
Thursday pm - purchase 25 euro Bayern ticket to travel from Munich to Fussen
Friday - If finished in time, take 2:05pm train back to Munich, using the Bayern ticket purchased the day before
Saturday - Purchase Bayern ticket for 2 people (32 euros) to travel from Munich to Salzburg

Option 2
Thursday pm - purchase 25 euro Bayern ticket to travel from Munich to Fussen
Friday - If not finished by 3pm, purchase new Bayern ticket for two people (32 euros), travel alone from Fussen to Munich
Saturday - Use Friday's Bayern ticket for 2 people to travel from Munich to Salzburg

If I end up needing to do Option 2, will there be any issues with just me traveling on a 2-person ticket from Fussen to Munich?

If I understand you correctly, I see a problem. The Bayern Ticket is good as follows.

• From Monday to Friday from 09:00 until 03:00 on the following day (that's 3 am). 3 pm would be 15:00.
• On weekends and on public holidays the ticket is valid from midnight (instead of from 9 am)

You'll need a new Bayern Ticket for Friday.

The ticket is also for 2-5 people traveling together, and you're required to fill in the names upon purchase, so yes you could well have issues with just you traveling on a two person ticket.

Yep, it is valid until 3 am. So really on ONE day. You got that totally wrong.

It is in general for 1 to 5 people (you can also travel as a single person.) If you start the journey as a group of 2 or 3 or more people you can always reduce the number of people later - but not increase.

Ooops, yes. I was thinking 3pm instead of 3am. So it looks like I'll need a new ticket for each day.

I wasn't aware that one person could travel on a Bayern ticket for two people - I apologize for my error. Thank you for the clarification Ingo.

It makes sense though given that the initial ticket costs more.