Just a casual word of warning re fitness expectations. In buying a road bike, you’ve done your chances of getting fitter/faster good, but… A huge number of people buy road bikes to complement a mountain bike, and then nimble about everywhere at a 14mph average for maybe a couple of hours tops, and don’t really notice any gains.
To get fitter/faster, go out with some roadie groups and learn about how to ride it properly, when and where to put the effort in and how/why it pays off, and learn to shut the pain out!
I bought a road bike for the same reason, and to be honest to start with didn’t really ride it all that far or fast. I’m on my 2nd now (and thinking about building a proper winter bike to keep the mileage up through winter) and have gone from those 14-15mph rides to comfortably faster. Completed a 75 mile sportive with 1500m of climbing at the weekend in 4 1/4 hours, average of over 18mph. Plenty of people are still quite a bit faster than me, but the point is its where I was compared to where I am now. A lot of it is learning just to block out the pain and pedal harder though!
And yes, I am definitely faster on an MTB as a result too…