] I wonder what Jane would've done with a Grand Tour?

Ah yes, I wish that she could have had the pleasure of seeing Paris and Rome!

It's possible that letters from James and Edward exists.
They would have gone back to them or their family after Mrs Austen had died. Part of the information we have about their Tours may come from such letters. Although considered not important enough or too private to be published.

I'm sure that young men on tour sometimes did things that was not suitable to write home about. They may have been tempted to get involved with women who were no ladies, if you see what I mean. The purpose of the trips was to give them a bit of life experience too.
Not that I think the Austen boys.. No, of course not :-)