Cupra – my wife and I bought a tandem for exactly the reasons you state and we love it. There is no way she would dare to go off road with me on a tandem so we use our solos off road. However, on road it is ideal. I never have to worry about going too fast, she never has to worry about riding too slow and we can chat as we ride along.
There is lots of good tandem advice on the web but my summary is as follows:
Firstly, your stoker must have confidence in you (assuming you will pilot). This means taking it easy to start with and listening to them regarding their preferred descending and cornering speed.
Secondly, keep your stoker happy. Agree on a mutually comfortable cadence, shift to a lower gear when they ask, stop when they want, freewheel when they want, etc.
Thirdly, keep your stoker comfortable. Fit a comfy saddle and suspension seatpost for them.
Once your stoker has confidence in you, knows you will keep them happy and will be comfortable then you will enjoy many hours riding together.
The other advantage is that it will make your solo bike feel ultra manoeuvrable when you get back on it after a tandem ride.