Regarding 1 there are mainly two options afair: CNC4Newbie slider and TBD CNC. Which one is better I can’t tell. I suspect both are (far) superior in comparison to the stock z axis.
Regarding the direct drive I think there is a kit. But I can’t tell you the ups and downs, I’m planning a self build one currently.
The DeWalt model coming with the xcarve is a DeWalt 611 (26200 in Europe).
Fusion is free for Hobbyist or small businesses below 100k$ p.a. I am using it since day 1 with my xcarve, never needed to pay anything since my xcarve is a hobby. If by some miracle I will be making 100k $ p.a. with my hobby, I will gladly pay the fee 