Do I really have to get a PC with Windows 10 in order to be secure, or is Norton security enough?
You should update to Windows 11 as Windows 7 is no longer supported by Microsoft and there are security vulnerabilities there.
Norton will still run under Windows 7 but you should be aware that you are not practicing good computing security by running Windows 7.
being you mentioned chrome i do believe that chrome will or soon will be ( not sure of exact date) no longer supported by chrome for updates ( whether or not will still function is another question)
windows 7 and now windows 8 are no longer getting updates , so would be wise to goto windows 11 ( would skip 10)