M17x R3, SSD questions

Current set up, Older M17x R3. started on Win 7 with A8 Bios, then after Win 10 free/forced update, the only way I could get this laptop to work was update bios in order from 8- A12. It figures with Nvidia/GeForce(wont recognize I have any Nvidia parts or software), somehow a powershell update killed my batteries ability to recharge & I have a windows antivirus update that seems to be the key to it all running in harmony.. Hoping the SSD & Fresh windows install will fix, stop or eliminate these issues somehow in the process.

Found a SSD on sale for 20 some bucks & figured since it was time to refresh my laptop why not try it. Ive had so many issues with this thing as of late due to updates, if this doesn't make it better Ill probably sell it which would break me so Im hoping for the best.

Questions/ Looking for advice on

Is there any write ups or advice for installing the SSD but keeping the OEM hard drive for extra space?

Has anyone figured out which bios will work with Sata 3 speeds? In my research all I find is people saying you can only get sata 2 due to various issues/pc set ups(mother board, bios)

Is it better to go with Win 7 or would win 10 Pro be ok? 

Looking for any suggestions with this process. While searching Ive ended up with more questions than answers. I also cannot seem to locate some of the more popular used write ups for step by step instructions. Theres more back & forth then Im comfortable with like how some people clone others swear only fresh Windows installs are best. Then Raid VS ACHI, or which bay to put the SSD in.