I am considering putting my Railways of the World collection up for auction and was hoping to bundle all the Railways games into one lot for ease of filling out the form, etc.. Is that possible? (I would think it would be, I just wanted to make certain so I'm not the auction problem child)

I am pretty sure you can, but if you don't put a reserve on it, the entire bundle can go for a very low price (possibly).  

From the Auction FAQ:  "Should I sell my stuff in batches or just piece-by-piece?Depends on the stuff. At the desk where you check in at the auction you’ll find expert collectors who will offer advice like this. (You may have a valuable collectible and not even realize it!) If you’re sure that some items are all common and related, it makes sense to group them. Some things should not be batched, such as unrelated items (a family game, a wargame, and a roleplaying piece), and games of higher value that will likely do better individually."

So it sounds like the answer is it is possible to do what you are proposing.  You could always contact them directly to ask for an official answer.  https://livegameauctions.com/contact/

You can bundle anything together that you want, but obviously the more connected they are the better.  If the expansions are relatively inexpensive (like say an event deck) I'd bundle with the main game.  Higher valued expansions I'd sell separately.

Keep in mind each auction is $2 + fees.

You'll need to determine before the auction how to bundle.  At the auction its too late given the cutoff for entry is 7/23.

Train games are pretty niche at the auction and have their own auction slot (30-60 minutes usually), but are typically well attended and train games  do reasonably well IMHO.