Offline testing while site is already running

Hi there,

I already have a running WordPress site, but I’d like to play around a bit with the layout of it so I was hoping to be able to do this in an offline environment. I know I can do this by installing XAMP or WAMP, but I have a feeling this is used more to create a site and then upload it, while I would like to just do some try outs.

So my question:
– is this the same procedure?
– what will I get by using something like XAMP: an offline version of my site or a blank WP blog?
– will installing an offline version affect my online site?

Thanks!