If you can believe the specs! My 100w Coleman (Sunforce) has 17.1 Vmp while my other brand made in India 100w has 18.8 Vmp. I have two of those latter ones for three 100w panels.
I tried their Vocs and Iscs in real life and got identical 20.5v (panel heating reduces voltage) and 6.2 amps so I decided they were in fact the same ratings. I run all three in parallel with PWM and get 18.6 amps as expected.
I tried them with MPPT and got about the same 18ish amps to battery (panel heating affects MPPT, but PWM uses Isc value not voltage)
I tried the MPPT with them in parallel and in series same conditions, perfect testing day, got the same amps to battery.
So IMO, just use those 50s however, and it will all work out.
