Been on Fellhorn several times, each time in summer. Took the Fellhorn or Kanzelwand Cable-cars most of the times but once climbed via the support road. Good traverse from Fellhorn to Söllereck, also traversed multiply.
Hiked from the trailhead to Kanzelwand, then up to Fellhorn and finally down to the middle station, total time 3h30. Very pleasant, not too hard, gorgeous views on a beautiful day.