I have the DropBox plus plan on my iphone. Can it also be used on my laptop (not an Apple)?

The Desktop app (which would also be applicable to laptops) is available for Windows, Mac, or Linux.

https://help.dropbox.com/installs-integrations/desktop/system-requirements

Yes, you can install DropBox for Windows and access the same folders as you can from your iPhone.

You can download DropBox here:

https://www.dropbox.com/desktop