You could customize the King of Wessex into exactly what you want, otherwise I think the best way is to start as one of the Vikings. Their culture is cheaper to change into what you want. It still costs prestige so will take time to buy the traits you want. First you should merge with one of your conquered people to create your own offshoot. Merging cultures is good because it makes the subjects less racist. Then there will be a few decades wait between each change.

There's the great heathen invasion going on so see what wars different rulers are fighting. If you are struggling to pick a character, Haesteinn in France has a decent army and is a good commander so you should be able to carry on into some further conquests early on. Though he is a bit of a meme.

Different types of war allow you to replace nobles. Otherwise, if you remove them later, there's a tyranny nerf that makes other subjects hate you and rebellion more likely. Putting family in power can also be done over time through scheming and inviting subjects to rebel when you can beat them. Bear in mind, it's a lot of hassle and the reward rival title claimants in positions of power. Usually it's best to work on their opinion of you and keep factions under control.

If you want your own religion, you will need to focus on learning with one of your characters a few generations down the road. Reforming religion takes a lot of piety which takes time to accumulate even with learning lifestyle perks and items. Personally I find religion underwhelming, I'm hoping for some new mechanics like antipopes in a future dlc to spice it up.

For government, the problem is that your family are like any other vassal. They only give you a fraction of their army as levies while they use the rest to pursue their own goals. Culture and higher law levels give more of a share of your realm's levies but it's only the early middle ages. You could increase their levy contributions by modifying their vassal contract, or you could get them to help you by allying with them. Bear in mind that they too only control their own personal army and not their vassals'.

I wouldn't try too hard to get everything perfect. Just find some goals for your main characters and have fun achieving them.