It sounds like you have a pretty functional system already, so all you would need to add to supplement your system with solar panels would be the solar panels and a charge controller.
Personally I would pass on the kit you posted. Looks like cheap no-name PWN controller and flexible panels. There isn't necessarily anything wrong with it but a more robust and efficient system can be built for about the same amount of money. An MPPT charge controller will be more efficient, and rigid solar panels are much more durable/long lasting and handle heat much better.
Also, if you think you might want to expand in the future, its probably better to spend more money now on a charge controller that gives you room to expand. 200W of solar is enough to maybe power your fridge if its efficient and charge a few devices on a good day, but not much more than that.
Watts are a measure of power. A 200W panel has a max power output of 200W in laboratory conditions, and will generate 200 Watt-hours
in an hour (assuming 100% efficiency). Watt-hours are a unit of energy (what your batteries store).
But as Ronnie stated, the rated output, is in near perfect conditions, and isn't a good measure of what you will realistically produce. 50-90% of the rated output is probably a more realistic range for most normal conditions. Expect flexible solar panels to be towards the lower end of that spectrum, if its warm out.
Depending on where you live
or travel you can usually estimate 3-5.5 hours of peak sunlight, more in the summer less in the winter, but its a decent ballpark estimate. Where I live, that number is 5 hours, so a 200W panel, operating for 5 hours, at say 70% of rated output, would generate about 700 Watt-hours per day.
This series of videos
is a good place to start learning the basics