You are better looking at TrueNAS Scale (Linux based) over TrueNAS Core (FreeBSD based) unless you have a specific requirement for it. Almost all development is going into Scale.
As a broad, general rule, stay away from any special devices or dedupe unless you have a proven need for them. SLOG devices may be helpful if you have synchronus writes but they should be specific hardware. explained in links.
BASICS
iX Systems pool layout whitepaper
https://www.truenas.com/solution-guides/#TrueNAS-PDF-zfs-storage-pool-layout/11/
Special VDEV (sVDEV) Planning, Sizing, and Considerations
Linking some other posts and whitepaper. They explain a lot of the items you are inquiring about.