This is why companies are using stretchable wind-blocking materials like Assos airBlock and Gore Windstopper X-Fast and X-Lite. They're nice.

The plusses of loose, non elastic hardshells are lower prices (older technology) and versatility in layering underneath for wide-ranging temperature variations. If you have a large wardrobe budget for diffierent conditions, including multiple jackets, get the new-tech elastic stuff, and a poofy old-tech GTX or eVent hardshell to wear 2-3 layers underneath for frigid conditions (if you're up for this kind of riding).

No single jacker--or any other piece of kit--will handle all conditions optimally, but you can always assemble something that works satisfactorily for the conditions in which you ride.

Basically, your greatest variety of choices is for 60-degree plus riding, this is what 90% of apparel out there is designed for. For 45-60, you can add arm and leg warmers to spring-fall kit, or go with light jackets or some thicker long-sleeve jerseys. Below that, go to tights. Look for Roubaix and windblocking panels. Get a windblocking jacket. Below freezing, you can either get very expensive cyclewear (where choices are limited because ridership plummets and with it the market for apparel), or look at alpine sports gear. There's a good range of body-hugging stretchy windblocking softshells in this category. Generally go down a size from your cyclewear--if you wear Italian kit, maybe two sizes.

A lot of online retailers have mfrs' size charts. If you do your homework, you can find mfr size charts for everything out there.

For rainwear, stretchy GTX has been under development, I don't know if anything is on the market yet.