Test site local or as subdomain?

I'm new to this, having "inherited" a ZC site from someone else who is no longer involved. As it is, the site is working fine, but I'd really like to start making some changes to it. What is the recommended way to do this, since I obviously don't want to be changing the live site.

Is it better to create a subdomain and do a fresh ZC install there? Would that interfere at all with the live site?

Or is it better to use xampp to do all the testing/designing on a local machine?

Is one way better than the other? Is one easier to transfer over if/when I get my test site perfect (LOL!)? Would I just be able to then replace the old site with the new fairly easily?

Can anyone offer pros and cons to local vs subdomain?

Thanks a million!

I've never worked locally. I do have Zen Cart unzipped on my computer and do my editing there, but I don't actually run Zen Cart locally.

Subdomains work fine. You need to create a separate database for the test site and install Zen Cart in its own folder. It won't interfere with the live site as long as it's kept separate (folder/subdomain and database).

Yeh i dont work locally either, have done it once just to take a screenshot but aprtfrom that i work live.

Quite often put up a Html holding page up so potential clients know im doing work on the site and that it will be unavailable at present.

If its a brand new site, usually work on own hosting or on a subdomain then transfer it over afterwards