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
Special VDEV (sVDEV) Planning, Sizing, and Considerations
Linking some other posts and whitepaper. They explain a lot of the items you are inquiring about.