Regarding warlocks, they are arcane casters. Any reference to them being primal casters is an error from earlier ideas about the class.
Woah. I thought it was the exact reverse. Earlier documents had some indications they were arcane, but all indications of that have been scrubbed from the most recent version of the primer and they are pretty solidly described as primal.
Pg 45 still says that warlocks with fiend or old one patrons are arcane, and all others are primal - which since the fiend and old one are NPC patrons only (pg 38) means that all PC warlocks would be primal.
Yes, you are absolutely correct. That's what I get for not keeping track of versions. My apologies for adding to the confusion instead of providing clarity. The only player option for warlocks is a primal caster. The other, non-player options, are arcane.