First of all yes, of course you are able to create mobile games with the Unity free engine. Otherwise it would be silly to have added a feature like that in the free version. In the past free versions there was limited access to the engine but still plenty of tools to work with and complete a game.
Unity changed its license since unity 5.0, they had to since they felt the heat from Unreal Engine 4. You can use the complete engine with all the features now as long as your company does not earn more then $100,000 / year. The only drawback I can currently think off is the Unity splash screen; you cannot turn it off. But if you are developing with it,then you should be proud of it and embrace that splash screen :).
Other then that, the pro version offers some extra things, as:
- Cloud building.
- Team Licensing.
- Access to Beta versions.
- Performance reports.
- Discount on asset store.
- Access to Unity source code.
Neither of these features important for a solo developer to build a game. Perhaps slightly when your game is near its final state when you want to test and they offer handy tools when your game is published.
Your final question is very much subjective. If you are really serious about creating games then you should grab the pro license in my "opinion". It gives you that bit of extra control and what is 75 euro / month for someone that is serious about it? I pay more then half of that for my phone each month.