I dev on both Windows (at home) and Mac (at work). We deploy and test to linux boxes. As long as git is installed on each machine, there are no problems. The only tedious part is getting everyone’s account setup and working nicely with SSH keys on all the machines they work on.
No, the subversion repositories can be stored wherever you like. It happens that in my case, I’m in charge of the web hosting for my company so I put it on there, along with the exports etc. I don’t do work for clients as such at the moment, just internal applications.
I use WinSCP to sync the webroot on my dev system with the webroot of my web server. Pretty basic solution, but I code alone so it works for me 