We will be in Austria and Germany for 5 nights in July. This is the Salzburg portion. Questions are bolded. Thank you!

Staying at Hotel Andra. Family of 4 with two teen boys.

1 - fly into Munich. Use Bayern Pass to get to Salzburg. Check into hotel, get groceries. Explore Mirabellgarten area and St Sebastian Cemetery.
2 - Fraulein Maria bike tour 0930-1300. Bus to Schloss Hellbrun. Use Guest Mobility Card.
3 - Lake Konigsee. Bus 840. Portion in Austria is free. Am I correct that 840 no longer requires a bus change in Berchtesgaden? And do I pay cash on the bus? I assume the driver reduces the fee based on the portion with the Mobility Card?
4 - Werfen Ice Caves, SOM trail. Use Guest Mobility Card. Back to Salzburg for Marionette show at 1930.
5 - Wolfgangsee or Hellein Salt Tour?
6 - Head to Munich for 5 nights.

I know I don't have time set aside for Salzburg itself but I figured we would do that in the late afternoon/evenings when we were done with our plans for that day.

Thank you!

Can't comment on the bus stuff but you have an uncommon itinerary, in how little time you spend in Salzburg, the town.

You may want to change the garden portion since you will see it on the bike tour. You are better off changing that with the castle and surroundings or more time in the old town.

We plan to spend time each evening in town. I figured an hour or two most nights and we will be able to see most things, though some may not be open. We tend to get up early, so by 4pm we have returned from our day trips

I actually tried a French-language AI assistant during my trip in Lyon. It helped me translate some complex menus and even explained local expressions I had no clue about. Really handy offline too with cached prompts

What, exactly, are you hoping to accomplish with this itinerary?

Am I correct that 840 no longer requires a bus change in Berchtesgaden?
No, sometimes a bus change is still required.
And do I pay cash on the bus?
Yes, you can pay cash on the bus. Cards may be accepted but I´m not sure which cards exactly are accepted. Cash is the better option in this case.
I assume the driver reduces the fee based on the portion with the Mobility Card?
Yes, correct. You´ll have to pay only for the German part of this trip. The Austrian part (from Salzburg to Zollhäuser) is covered by the Mobility Card. For the German Part (from Zollhäuser via Berchtesgaden to Königssee) you´ll have to buy extra tickets (2€ for adults and 1€ for children - single way).

Wolfgangsee or Hellein Salt Tour?
It depends on what you would like to see. Wolfgangsee: great nature, wonderful scenerye. But many tourists down there. The small cities there are overcrowded during holiday seasons.
Hallein: the salt tour is very interesting. But there´s not much more to see in the little town of Hallein. Maybe this gives you a bit more time for exploring Salzburg. Visit Hohensalzburg and walk to the Mönchstein. Go down to the city center there by using the public elevator. Have a drink or a coffee in the roof top Cafe of Hotel Stein.... There´s so much to see in the city....

Thank you ml871. That was very helpful. I appreciate your response!

I'll run the salt tour by the kids and see if they are interested. If not, we can do a Salzburg day.

I did a salt mine tour from Salzburg which was a lot of fun. We had to get into suits, then rode a little train into the mine and back. We walked around and then got to slide down two rails. It was like being a little kid again riding down a staircase railing. My sister bought the picture of the two of as she said she’d never seen us so happy together. I think it was a half day trip as I don’t recall it including anything else so you might want to check as you could do Salzburg after.