[Closed] how fat can i go on a 29er kona unit if i use 26ers and ditch the coaster?

if i run 26inch wheels on a 29er kona unit can i go fat? if so how fat. ive got 2.4 rubber queens which do come up more like a 2.7" but would like to experiment with some proper fattys :D was planning on getting some slick 29er tyres if anyone can recommend some for commuting and some fat 26er tyres for off road fun! would the geometry be affected too badly running fat 26ers? also ive got a 3-speed nexus with coaster brake and cannot get on with the pedal back brake. can i disengage it if i want to carry on running the 3-speed. ill probably do away with it if im having two wheelsets as it will be easier to swap between wheels if i run a standard geared set up and i`d have to run different rear brakes to swap 🙁