My tours in Budapest are primarily walking tours which are combined with using some public transportation occasionally. However if you can not or would not like to walk, it is possible to have the tours by car or van.
My recommendation is to do a walking tour as that is the best way to discover the city. In this case the tour is a combination of a walking tour and using some public transportaion.
If you feel that a full day walking tour would be too much to walk, you can break it down into two half day tours. In this case one day can be dedicated to the pest side and the other day to the Buda side. If you do not even have the time for a full day tour we can visit the highlights of the city in a half day walking tour.
An overall tour of the city can be done in either a full day (7-8 hrs) or in two half day (4 hrs) tours.