Is upsized reactor allowed for the comparitively less motor HP?
The input reactor is only for reducing the harmonic content (distortion) of the input current. Harmonic content can interfere with other equipment connected to the same distribution system. There will be no problem at all for the VFD or motor. There is not likely to be any difficulty with other equipment either. Many VFDs are installed without them.
The output reactors are for protecting the motor from voltage spikes generated by the VFD waveform. The sizing is not critical. You probably should not worry about those either.
In both cases, the disadvantage of the reactors is that they introduce a voltage drop and reduce the voltage available to drive the motor at full speed. They are usually sized for the maximum impedance that the VFD manufacturer estimated is tolerable in terms if the added voltage drop at rated VFD current. Both the input and output reactors are probably sized for a voltage drop of 1 to 2 percent of the 480 V input and output voltage. If the VFD has some AC or DC reactance built in, they would recommend less external reactance.