Sure all 3 have phenotypes which tend to be prevalent in their respective countries, with some overlap.

For instance the British tend to have lots of super pale skinned people with pale blue eyes but dark hair. I suspect this had less to do with it being a genetic advantage involving vitamin D absorption and more to do with it being seen as aesthetically pleasing and a sign of purity or virtue, or possibly even having some pagan religious significance among the celts. You also see lots of brits with these hawk like noses that seem to be somewhat unique to them, especially among the upper classes, along with very fine angular facial features. There are other phenotypes you see as well there that are somewhat unique to Britain, like the ruddy complexion and slightly thicker/stockier type that is hard to describe.

Germans tend to be more of a mix of Scandinavian phenotypes and central and even some eastern European phenotypes. The French are a mix of just about every phenotype in Europe, the prevalence of which can vary depending on what part of France. The Stereotypical French appearance is of course slightly tanned skin, light brown eyes and dark brown hair, but you also find some with a very pale appearance but that tends to tan better than the Brits. France produced a pretty significant number of great scientists, inventers and thinkers, and in ww1 the French proved pretty adept in countering German military technology and tactics and often outsmarted the Germans at times, which is no easy feat, so I wouldnt discount French intelligence. Of course the France of today is vastly different than the France of the past.

As for IQ. Im not a big fan of IQ as the end all be all measure of cognitive abilities. You can have a group that has a lower average IQ score but is superior in some aspects of intelligence that arent as heavily measured on these tests. The Germans for example have always been renowned for their mechanical aptitude, and I doubt a lot of that shows up on IQ tests. Ashkenazi Jews on the other hand tend to be very good at some things that are heavily weighted on IQ tests(and which are more likely influenced by environment), but perform more poorly on things they dont measure.