Great job, I will give it a try. As I'm more interested for personal use, can it help me find the best WiFi channel to use for my network, as I live in a dense populated area?

Yes - by telling you what ones NOT to use. Click audit and then Wi-Fi Checklist. Choose your network, and then it will tell you if you are on a good channel or not, automatically!

Is that a feature of the $20 plan? Or only the $50?

Both will tell you - the $50 one will be much more detailed... but both give you yes/no feedback.