Or, will I need Windows for Linux to run?
No.
If you want to run just Linux, it should be pretty easy-peasy to install just following the defaults in the installer, and making a couple of choices there, when available.
By the same token, if you prefer to dual-boot, similarly easy-peasy via the Installer. An advantage with that choice might be that if you find it is taking a while to work efficiently with Linux, you can bail out, reboot and choose Windows.Then when you are comfortable with Linux, blow away Windows.
There are virtues to both arguments, but you must make the choice.
While you think about it, have a check here
https://www.notebookcheck.net/Lenovo-Flex-14IWL.431888.0.html
and tell me if there are any significant differences with those specs and yours.
The main areas of interest to me are the 16 GB RAM, and whether it is just the one drive, 256 GB Solid State, or otherwise.
I have a 19.3 Xfce same as yours on USB stick, and can show you some screenshots of the install process when the time comes.
You've seen that there are others here ready to help if I cam catching zzz's, half a world away
Cheers
Wizard
BTW for other Helpers - Clement Lefebvre and his team at Mint decided (for unknown reasons) to stop shipping GIMP installed by default, with 19.3 - for using an app named Drawing instead. However it is still in the Repos as we have seen with the OP's Synaptic, so can be installed on her "finished product".