Haven’t played a dedicated experiment game, but some thoughts:
If you’re to play very aggressively, you can end up trying to pre-emptively close (or block) any road that looks like it might get long (more than 4). The flip-side of this is you end up with lots of short roads, thus making the RB worth more…
On one occasion I was able to manufacture it so the piece that closed the longest road (10+ tiles which was shared) would also close my major city – this added to the dilemma of my opponent insofar as if I got the tile (FRCC) I’d close both and get mega-city and RB, so it was worth the risk to my opponent not to close it (which they didn’t). I never got the tile, so the gamble paid off for them.
RB has the same-ish dynamic of Trade goods in this respect, helping your opponent close a feature in order to get points at end-game.
Without the builder, I personally view Inns as an added bonus to a road, rather than something I would actively pursue.
In combination with the RB, they become fairly risky in terms of being trapped and not likely very valuable unless you get an inn that closes a road (as opposed to being on a road corner or straight).
I guess the key part is who currently has the RB. If you have it, you can play Inns to increase value on short roads and (try to) cap anything that gets remotely close to taking the RB from you. If you don’t have the RB, unless it’s a quick way of getting 6 points rather than 3, I think I’d dump them somewhere useless.
With only these expansions, RB would likely be worth 10-20 points at end of game? There’s 6 Inn’s in the expansion, in a two player game, if you got half of them, you would only need 3x 3- or 4-tile roads to get the equivalent points. As soon as a road gets to 6- or 7-tiles long with an inn on it, I don’t think it would be worth capping your opponents but should try to be trapped ASAP.
It does risk slipping into 50:50 results however – if your opponent closes the road, they get the Inn points AND the RB (possibly a game winning 40 points), if they don’t, you win. I’ll try it in the next real-life game I play
In combination with other add-ons, notably the Builder or Abbey (or indeed both) it can become very strategic; with the builder on the road and a road 1-tile shorter than the current RB-winner makes for some very tense moments. Similarly the Abbey can be used to cap a road which your opponent has trapped (I’d already played mine in the previous example).
One thing I do like is once you have the RB – you then start building multiple roads to make it more valuable. It’s also quite fun trying to subtly steal the RB back by expanding farms/cities which “happen” to have a road next to them… (The same applies with 2-tile cities and the King).