How should I run power wiring and Cat-5 to the perimeter of my huge yard?
Trenches are hard/expensive.

Conduit is inexpensive. Having dug the hard and/or expensive trench, investing a tiny bit into having conduit in the trench so you never have to dig that trench again is just sense.

Direct burial is silly. It's especially silly the second time, when conduit the first time would mean no need to dig again. It's a short-term savings that often isn't even a savings (conduit + wet-rated outdoor wire is not infrequently less expensive than direct burial outdoor wire.) You do need wet-rated outdoor wire - all conduits outside are assumed by code to be wet, and the assumption is usually correct - condensate will do it if nothing else does.

Depending on what security cameras you get, ethernet can be the power wiring (PoE cameras)