HE can handle a lot of automation but you need to pay attention of device themselves. Because of different frequencies, some devices can be used in USA/Canada, but not in Europe. HE is usable in any countries (USA/Canada/Europe/Australia/...)
If you order automation devices (ebay by example), you need to be sure that the purchased units will work in France.
About audio, I think you can build an entire system with the rights units (Sonos are good speakers with embedded automation, wired and wireless), Ikea's Symphonisk are made by sonos and provide good quality units for good prices too.
I'm a kind of newbie with HE (not with automation) and I can't give you more precision about what you define as "whole home audio system".
I managed to build very easily a nice (vs whole) audio system for almost nothing:
some symphonisk's speakers, some Google Home speakers, a windows W7 with a file server that's able to feed my phone. On my phone a very nice app (bubbleUpnp) that allows me to redirect any played song/playlist to any speaker of my house. And I have with that simple setup a way to reach my goal: play my music on any room with speakers.
Working in my garage ? I can listen to rock music in my garage,
Laying on my living room ? I can listen to soft music in my living room
Reading a book on my bedroom ? I can listen to classical music in my bedroom
It's enough for me. And without home automation (HE or alike). Maybe not enough for you.
I'm sure you'll receive more answers here. If you need more info of my setup, you can PM me if you want, in french if it's easier for you (french is my mother tongue).