I haven't taken a tour in that area, and I visited Figueres (while staying in Figueres) and Cadaques (while staying in Girona) on two separate trips to Spain. However, you should be able to combine the two via public transportation if necessary.
There are both fast trains (to Figueres Vilafant Station) and slower trains (to Figueres station). The Dali Museum is located between the stations, quite a bit closer to the latter. A city bus runs between the stations and within a few blocks of the museum. It seems to be timed to the trains at Figueres Vilafant, but in my one experience, the bus didn't wait when the train was late, so it was necessary to walk about a mile or hope there was a cab waiting when you exited the station, or plan to call one. While a tour bus would remove that uncertainty, note that a bus would be a lot slower than a fast train in covering the ground between Barcelona and Figueres (and that difference would exist on the return trip, too. The fast trains take 55-57 minutes (tickets cheaper if purchased early); the slow trains, at least 105 minutes. ViaMichelin.com estimates the time by private car at 99 minutes, and loading a tour van would add extra time.
There are buses from the Figueres station to Cadaques; the route is scenic (and curvy). The bus station is higher than water level, so it's a downhill walk upon arrival and an uphill walk when you head back.
In case you are also interested in the Dali house in Port Lligat: I saw a sign pointing the way from the port at Cadaques; I believe it estimated 20 minutes. It's reportedly a bit shorter walk from/to the bus station.
Other bits of info that might be helpful:
The Dali house in Port Lligat has limited capacity and sells out. The ticket must be purchased in advance.
The Dali Theatre-Museum in Figueres is popular but isn't as difficult, ticket-wise; however, there can be a ticket line, and individual time slots definitely do sell out in advance--inconvenient when you've got a busy schedule on a day trip. Therefore, you'd be very, very smart to get this ticket a a few days ahead. (In May 2019 I bought mine the day before, but tourism levels in June 2023 may well be higher.)
A French bus tour arrived at the Dali Theatre-Museum 20 or 30 minutes after I did. They left long before I did, and I am not a fan of surrealist art. Do you want a tour operator to decide how much time you spend at the museum? It's not like you can just walk back to it from your Barcelona hotel the next day. I am very doubtful about using a bus tour to combine two or three Dali sites if they are really important to you. On the other hand, if you really want to include the house in Port Lligat, a bus tour would simplify the logistics considerably.
The ticket to the Theatre-Museum in Figueres includes the Dali jewelry collection, located nearby. It is fabulous. It's doubtful a tour will allow time for you to see it. It might take about 30 minutes or so.
Cadaques is a very attractive (though now touristy) former fishing village. Figueres, by comparison, is short on charm; you needn't plan to spend much time there beyond what you need for the museum and jewelry collection.
My recommendation: Spend 2 or 3 of your nights in Girona, which is much closer than Barcelona is to Figueres and Cadaques. In addition to reducing travel time, it will save you a bit of money on transportation since you will make two rather than four trips back and forth between Barcelona and Girona. Girona is a very pleasant place to wander in the evening after your hard-core sightseeing is over. You can easily press on to Girona on your arrival day, when you may not be in great shape to tackle heavy-duty sightseeing. (I wouldn't pre-pay for a tour in Barcelona that day in any case.)
I think you need more time for what you plan to see. Five nights with 3 side trips is shortchanging Barcelona.
