The Saxons came from Germany, as did the Celts before. The others came from northern Europe and had been heavily influenced by the Celts in the past. This meant that the Saxon and Celtic cultures were fairly similar in many ways. There is an excellent description in one of the fairly modern "Arthur" books, perhaps in the Pendragon Cycle but I am not sure, of a Celt describing how the Saxons ape their own customs, basically it goes like this - our maidens have hair like flax, theirs have hair like straw; our bards sing heroic tales of old, theirs caterwaul of the grubby deeds of unimportant forebears; our Heroes go into battle with the Hero’s Battle Rage, theirs are brutes who lose all control of their actions. Pretty similar if you ask me.
The Saxons have a Heroic Tradition of warriors, they have a tribal culture with the Chieftain and his thanes being the central point, they have berserkers and bards. All these are shared by the Celts. The Saxons worship a different Pantheon, but it is similar enough for Druids to gain spells from the Saxon Gods.
The Saxons worship Woden, Frigg, Thor, Wayland the Smith and Tyr. Angles and Friesians possibly worship Odin , or a similar god, but this is basically the same as Woden. Use the Vikings Pack for Saxons, as they are fairly similar, although the Vikings did not have Wayland.
The Angles, Saxons and Jutes spoke different languages. This makes it harder for them to communicate with each other, although many also spoke Latin. None of the Saxons were Christian at this time, so all would be pagans. The Saxons did not have Druids, preferring only to have priests of individual deities.
All the Anglo-Saxons kept close ties with their kinfolk on the continent, exchanging warriors, tribute and money. This is driven home by the legend that Arthur conquered Scandinavia after he freed Britain - he obviously followed the Jutes/Angles back to their kin and continued the Conquest. This is such a good idea that I included it in my timeline.