Why not Barb as the lowest if I may ask? Rage and go hit stuff, seems like the simplest class to play to me.

I like this summary of each class, it includes a 'difficulty' rating for each:

link

I don't see a specific rule for this, but I would just let them ignore the restriction of picking a certain number of archetype feats before selecting a new archetype. There's nothing preventing you from picking a 2nd level feat at level 4.

https://2e.aonprd.com/Rules.aspx?ID=1333

Never enough. When I die I want my kids to be burdened with wondering what the heck to do with dad's dozens of boxes of rpg books.