3s will charge quicker because the voltage is lower, with the 4s, your going to have to up the charge voltage to get them fully charge. If you build it yourself 3s will be easier to build. 200 ah of 4s will be many more cells. My 94ah battery pack was 156 cells. Myself if I had to build another 18650 battery pack I would use 3s, thats just my preference, you can charge with available chargers and they run all my stuff including my inverters even when I got it down to 30 percent, I never needed a booster for it. But for a 4s battery pack you will need something to take down the voltage, fans/lights don't like voltages above 15 volts, even 14 volts will be pushing it. The goal zero lithiums are all 3s.
With 4s, if you use your current chargers, they will see a full battery when the battery reaches 14.4 volts and probably reduce amps to float which will be less then an amp, you will have to hope your chargers can have the bulk voltage raised above 15 volts. Also voltage drop between chargers and battery might not let you get high enough to give them a good charge.
With 3s you need something to monitor your balancing everytime, it not something you can neglect. I wouldnt rely on the BMS to stop the charging everytime. And if you will be charging at high amps, I highly recommend active balancers, they will keep up with your charger (balancing at up to 10 amps). Active balancers cost about 25 dollars per cell, you need 3 for a 3s pack, you can find them at electricarpartscompany. I use them on my 4s lifepo4 pack that had balancing problems but they also work on 18650. Picture of my 4s active balancers.
active balancers.jpg
) and it will weigh under 60kg/120lbs. it could power the starter motor on your generator for 3~4 hours non stop.
