Sync up localhost copy of my website to the online version

I create my websites on my PC using Xampp localhost. Then when I am ready, I upload to the server.

That all works fine. I have a particular site that has been up online for several years, and all new edits to the site have been done online.

Now, I want to get my local copy of the website to be exactly the same as the online one. (I need to do some local testing.)

What is the best way to get my local site synced up to the online one? I know how to download all the WP files, and I know how to backup the online database.

Is there an easy way to just update my current local copy (eg: found at ‘http://localhost/LocalSite/LocalSiteWP’ folder) with the new files and database?

Or is it better to just start with a new folder like eg: http://localhost/OnlineSiteCopy/OnlineSiteCopyWP, and just following instructions on how to create a local copy of your online site, including creating a new database, etc?

Can someone give me some direction on this – which is the better, faster route?.