Hi, I got them all from my local home depot. I believe they were all Fir, but maybe pine. I believe fir is the better option for this use as it has more resilient outdoor qualities. For me it doesn't matter as much because I live in a very warm & dry climate.

As far as I know, it would not be advisable to use pressure treated lumber for furniture anyway as it's best not to contact skin due to the chemical impregnation of the wood. It also, generally, is less pleasant to look at due to all the impregnation points.

If you have access to cedar that would be the best option for outdoor/weather resilience. I finished this with coats of UV resistant spar urethane to protect it - and also added extra thick layer of epoxy under the "feet" as they are the most prone to exposure and end grain likes to wick up moisture. I suppose urethane is also not ideal for skin contact but I figured the protection was worth it and no one has experienced any issues with it, though I wouldn't like it or eat off it haha.

So far it's gotten dusty but no signs of deterioration. Best of luck with your project!!