Will I still need EasyStart™ if I have a bigger generator or parallel two generators?
That depends on how big a generator and what you want to run at the same time. Without EasyStart™ the start surge is huge. Generators respond to this load by slowing down and reducing the voltage to the air conditioner. If they slow down enough they go into overload and the air conditioner won’t start.
Air temperature also affects the air conditioner. Higher outside temperatures raise the refrigerant pressures causing a higher current draw. We have had some customers with Honda EU3000iS generators tell us that the generator will not start the air conditioner reliably when temperatures get hot. Most 4KW generators will start a single rooftop air conditioner reliably but that’s a lot of size and weight.