Need practical advice on solar system

How some personal experience. Send me a PM and I'll respond

I know this is a really late answer on your post, but as there are few posts in this section and you didn't get answers to your questions so far I will give it a try.

IIf you are sure that you will never increase your solar array you could do with a 10A controller. The 20A will give you a lot more headroom and also a possibility to expand, so if the price difference is not too big I would go for the 20A controller.

As for batteries the best is batteries that are meant for deep cycle, those are typically labled something like recreational use. Typical uses are in golf-carts, trailers, boats, ...
Usually they are only slightly more expensive that a normal car battery.

The amp-hours of your battery bank depends on your intended usage.
A few general assumptions: Aim to never drain your batteries lower than 50% (it will save battery life and give you some room for margin).
Most people consider worst case is complete cloud cover for 2-3 days (no electricity from solar panels).
What battery bank capacity will you need to cover your needs?
Personally I use a single 100Ah battery (about the biggest that is reasonable to carry alone) and I only have 60W panel.
Do note that the way I think the capacity of the battery bank does not depend on the watts of solar panels.

For low power appliencies I use normal car cigarett lighter output and USB output.
For more demanding output, like an inverter I connect it straight to the battery.

For cabling etc I choosed a switch panel intended for boats where each output has a lighted switch and a fuse with reset button. It is always good to have some kind of fused connections on the output when dealing with electricity. 

As far as the cabel diameters goes I will let an American answer as you incist on measuring cables in a strange fashion.

My advice is to keep it simple to start with, so the hurdle of starting does not become a major issue.