Group policy is the most important to me in win-10 and only the pro version has it,
This allows the ability to block some of the items I find most annoying like Bing desktop search = web search suggestions from the Cortana search box on the taskbar or with Winkey+S keys and type for a local item/ program/...
You can also block Cortana/.....
Without win-10 pro you really can't block anything so you better love Bing/ Cortana/...... because home premium turns into 10 Home very few built in ways to get around the above.
Downgrading is not a very good idea seeing as the entire 10 is new and so is all of the processes
System restore has always been buggy at best so I don't see that as being improved on there's no incentive for M$ to do that they are pushing win-10 not rolling back to win-7
Best thing to do is create a reliable system image and recovery disk
Imaging with free Macrium
Otherwise simply join the insiders and use 10 for free and keep your original win-7 install,
I would do it on it's own hdd or ssd and never let the two hdd's meet
In other words remove your 7 install,
Then install a new hdd and install win-10