For hiking in the south of France in summer, I assume you'll be at some altitude, so layering is indeed a good idea.

I love Coolmax turtlenecks & light polarfleece (200), under a light rain jacket. Polarfleece isn't compact by any means, but you could wear it on the plane, or use one of those squeeze-the-air-out bags to mash it down. Coolmax (not the altamax which is heavier) will give you a good wicking layer for close to your body, but even in warm temps you'll be comfortable. You also could consider the zip-off-the-long-legs pants to give you flexibility in meeting temp variations by having long pants & shorts all in one garment.

On some hiking trips, I use a multi-zippered pocket vest instead of a backpack. I can cram almost as much in my vest! Course I look like the Michelin man, or the Staypuf marshmallow guy. Oh well.

For footwear for hiking, I'm keen on the shoes sold as trail runners. They're NOT white, & some models will do nicely for urban walking or mountain hiking. I also wear these on the plane because of the bulk. My faves are actually Goretex & therefore waterproof, as I have zero tolerance for wet feet for more than 10 miles!

Gail In Eugene