Train from Salzburg, Hbf to Heidelberg, Germany

Maybe not ideal, but not terrible.
Bring food and drinks and enjoy the scenery.

Did you even had a look at any map? Even if you go the shortest, but must boring route, by car, via the Autobahn, it is more then 5 hours drive. And you have to be very lucky not to come into one of the always happening traffic jams. Then it could take 6 hours or more.
So the train is the fastest one.

Thank you for your suggestions.

Basically you have two routes, west or north. To go north you'll have to go to the Munich train station and then board another train, ideally the ICE to Wurzburg. This is pretty easy to do. The best westward option is the ICE you've indicated. If it seems like a long trip just plan to get off earlier. But I'd stay on to Stuttgart at least, because it's difficult to get through that city on anything other than an ICE.

If you do decide to get off and explore, Augsburg and Ulm are interesting cities, and Chiemsee is beautiful.

It looks as though an option would be to take the ICE 116 from
Salzburg Hbf departing at 2:00pm , arriving in to Heidelberg at
6:44pm. It is direct but has 10 stops a long the way and is a 4 hour
and 44 minute train ride.

To be honest, that sounds like a lovey train ride. Why are the 10 stops a problem? It is exactly because trains make multiple stops that you have a direct train from Salzburg to Heidelberg.

However, there is nothing against just going all the way to Rüdesheim. I do not get why the train ride is an issue. Train travel is a lot more comfortable than air travel, so if you are fine with the 8+ hours it takes to get to Europe spending 6 hours on a train should be easy.

Thank you, Wengen! (Much better than, 'Did you even look at a map!') and I agree.

We will take the ICE 116 departing at 1400. It will hopefully go quickly since there are stops along the way and we can look out and observe!

Now-another question:

Should I purchase these tickets before we depart from the States or can I purchase all of them when we arrive at the FRA airport?

Furthermore-can you purchase the regional trains in advance or just the ICE trains? Would anyone recommend first class vs second? I've been on 2nd class and they seem 'fine with me?' However-since we are going a longer route (4.44 hours) it may be to our advantage to be in first.

Thank you again!

You can buy tickets in advance, and you can buy tickets at the station. And that you can do even on the day of travel. Just going to the station, buying a ticket and taking a train is how trains work.
However on long distances you can often get significant discounts when you book in advance.

And when you book train travel you book end-to-end. Tickets are in fact for a route, not a train. So you buy "Salzburg" to "Rüdesheim" for example. The ticket then covers the route. Normal tickets are flexible (allow you to choose which trains you take) but discounted tickets will bind you to a particular train for the long distance segment.

If you look up prices on www.bahn.de you will see different prices. "Super Sparpreis", "Sparpreis" and "Flexpreis.

Flexpreis is what you would pay on the day itself, and you can just take any train you want on the route. The others come with discounts and restrictions. When purchasing tickets I would also buy a resevation. Reservations are not included automatically, you need to purchase them.

This has been extremley helpful!

A big thank you!

Tracey