Each nation had a very different way their squads were set up ill give examples:
German and British squads were identical early war the both were bilt around the Machine Gun, both sides had a squad leader issued a Submachine Gun, a Machine Gunner issued a Machine Gun, and a lot of rifleman issued a Bolt-Action for self defense and to provide ammunition for the Machine Gun.
Soviet squads early war were similar to German and British but with 2 machine gunners, 2 submachine gunners, and a squad leader issued a Submachine Gun along with 6 rifleman that might carry ammo the automatic weapons, but soviet squads get interesting later in the war it went to full squads equiped with only automatic weapons like Self loading rifles, Submachine Guns, and Light Machine Guns.
I could list all of them but it would take a while, Gaijin please get this right