If you want to see a lot of places in a little time (whether several countries or several cities in one country) , a tour (guided or un-) is an excellent plan because you have door-to-door transportation. Most of the stops are 2 nights, (maybe one or two 1-night) and on the longer tours, there may be one or two 3-nighters. Each change day leaves you with an average of 1/2 day to sightsee (some rides may be shorter, but some will be longer). Read the itineraries for any tours you are interested in. They detail not only the sights but also the time on the bus and the amount of free time. Bus time is an opportunity to rest and relax between intensive days of touring and enjoy the scenery, catch up on sleep, journaling, get to know your tourmates, and make plans for your free time at your next destination. On guided tours, the guide often uses bus time for more guiding, discussing local history or customs, for instance.
For someone who hasn't traveled in Europe, door-to-door transportation can be a real perk. You don't have to navigate train stations on your own and you don't have to find your hotel and figure out the local buses and trams. Even on the MyWay tours, the tour escort will explain it all to you and probably take you on an orientation walk when you get to each location.
Other advantages to a tour are traveling with a like-minded group of people, having others to share the experiences, wine and dine with, and get to know. RS guides are almost always top-notch and may include "backdoor" experiences.