Is it complex to compare the traffic rate by numbers and percentages (I mean mobile vs desktop, is the chart there necessary?)
Answers: 1. You will get previous week but not older - not possible to fetch older data.
2. You can try 14 days for free to see it by yourself - there are no credit card charges and requirements, after trial expires, you will be move to standard free version.
What Pro Includes?
More depth insights of your Bounce rate: what pages have highest bounce rate, what devices people use that causes highest bounce rate, etc. It also includes goal tracking feature. Most trending descending pages. And more. I can explain it in chat, but I recommend to register, since it is free and see it by yourself :)
3. There are not a lot of competitors that do exactly the same. The advantage that product has - its simplicity and user-friendliness.