When you connect different type of panels in parallel, all the panels can only output the voltage of the lowest voltage rated panel. So…If your 120 watt panel operates at 20 volts and your 60 watt panel only operates at 15 volts, both panels will now operate at 15 volts degrading your 120 watt panel output. If the 60 watt panel operates at a higher voltage than the 120 watt, the 60 watt panel will now operate at the lower voltage of the 120 watt panel. If the voltages are fairly close, not big deal. If they are far apart you will not get the benefit of the additional panel that you would think. Basically add the amps of both panels and times that by the volts of the lowest rated panel and that will give you your potential wattage. X that answer by 80% and that will be more realistic in the real work under ideal conditions.
With regard to what happens if you over amp the EB70…The EB 70 will not allow any power over 8 amps and no damage should occur within a reasonable over amp situation. The Mppt does not not throw away any amps over the max of 8, it simply does not let in any amperage greater than 8. I personally would not be comfortable feeding it more than 200% of its max amp rating.
The only way to get close to the 200 watt max input is to have the voltage of the panels in the high 20s with 8 amps of current. Unfortunately, the practical max is going to be in the 150 to 165 watt range under perfect conditions.