Your fundamental understanding of the math behind calculating drive speed is flawed.
the equation is
(wheel dimeter)(pi)(wheelrpm))/60
this gives you inches per second. as you will notice if you run a couple calculations you can get similar speeds by just changing hte wheel rpm and wheel size. for example,
(3.25)(3.14)(360))/60 = 62 ish and
(2.75)(3.14)(450)/6 = 64.5ish and
(4)(3.14)(300)/60 = 63 ish.
this is jsut a really small sample but as you can tell by changing wheel rpm through gearing or chaning the wheel speed you can get any linear speed you desire pretty much. All drives with similar speeds have similar torque. The linear speed of the robot and the torque the robot has are inversley proportional for the same amount of motors. this means that for more lienar speed, ie 100in/s you will have much less torque than 50in/s for the same amount of motors. The wheel size realisitacally has no effect on this.
if you were theoretically running the wheels all at the same constant RPM, ie 200rpm, then the 2.75 wheels would have the most torque and the 4inch would have the most speed because per revolution the 4inch travels much further due to its large circumference.
check out this thread and look at what kind of speeds you can run keeping in mind higher linear speed means less torque for a constant amount of motors.