Pressure treated wood can be difficult to work with, due to being saturated with water/chemicals e.g., when bought from a big box store.
The moisture will dry off, but if you have cut the pieces made the joints etc, while wet, then things will not fit once the wood dries.
If you do make with pressure treated I would use a stain rather than paint. Some treated wood make not take a paint. Also the paint will crack if the treated wood shrinks due to trying in the summer heat.
If you are intending to paint, why not use 2x4 hem/fir? The paint will be the weatherproofing. Just keep the feet off the deck with rubber buttons.
Consider a design with mechanical fasteners. Even epoxy will fail if the wood shrinks in the summer heat.
Cedar looks great when new, but can crack and cause splinters.
If you want a naturally resistive wood, consider mahogany or white oak. After all whiskey/ wine barrels are frequently made with white oak and they last for a LONG time.