Last year for a while I was using two 20a PWM controllers on the one bank and they acted as one bigger controller adding their amps just fine.
This year for a while I had one PWM Solar30 and one MPPT Eco-W on the one bank (both set to 14.8) and they too added their amps just fine.
JiminDenver of course uses dozens at once, no problem :) As far as Bulk or Float, can't say since my Eco doesn't do Absorb, just drops to Float at 14.5 when batts hit 14.8 so that left the Solar30 doing it all at 14.8
Jim can give the play-by-play with two Eco-Ws.