Can I install W7 on a OEM W10 laptop?

There is no harm in giving Windows 10 a try. Especially if the PC comes with it already installed. You can still log in with a local account if you want. The Store and some Apps won't work, but if your never going to use them anyway no big deal. It does cripple the OS some, for me it would anyway as I use some apps. I also use the sync feature with my Microsoft ID. Look through the tutorials section and you may find ways to do a lot of what you want. Some things have been moved to Settings etc. Windows 10 does take some getting used to, especially if you have never used Windows 8 or 8.1. The current Windows 10 install media from the Media Creation Tool will read and use OEM embedded keys. You could clean install if you wanted to, to ditch all the factory installed bloat. First thing I would do is create your recovery media. Then what ever happens, you have the option to put it back to factory condition. If say you need to have it serviced or return it. Once you get it, then go hunting for Windows 7 drivers if you think you may go down that road. For me it would be a step backwards but that doesn't mean its not the right move for somebody else. The first hurdle is going to be buying a Windows 7 license if you chose to go that route. The second hurdle may be getting all you hardware working. Hard to say at this point. I hop it all works out for you which ever way you go.

Forgot to post this link in my above post, It's a link to the Windows 10 tutorials section of the Windows 10 sister site.
Windows 10 Tutorials
I go by the same username there, and on Eight Forums. Lots of people there to help you if you decide to give 10 a try. Many members here are also members there like I am.