Only with 1GB RAM, your laptop may be less powerful to run under Windows 10. If it is sometimes slow with Windows 7, then it is recommended to upgrade to at least 2GB RAM. Here are the system requirements for Windows 10.
To upgrade your laptop to Windows 10, download and run Media Creation Tool. Next, select Upgrade this PC now and choose Keep personal files and apps. The tool will check if you're ready to upgrade and install Windows 10.
Note that you can revert back to Windows 7 within 30 days after the upgrade. To do so, go to Start > Settings > Update & Security > Recovery. In "Go back to Windows 7", click Get stared.
Practically even a 2GB RAM is less for Windows 10. It should be at least 4GB. And space requirement I would suggest 40 GB. Otherwise you will face problem during regular updates. Regarding Free, Yes Windows offer of 'free upgrade from Windows 7 to Windows 10' is still working.