Unless you are growing water or bog plants, you need bottom drainage or weep holes at the base of the planter. Otherwise, you want to fill the planter with a uniform mix of potting soil - no drain rock at bottom, no barrier, no garden soil, just a good quality potting soil. This looks like an excellent situation for some type of bamboo - the planter is a bit too restrictive for much else that will develop any height for privacy. Equisetum can work also.

In terms of human and plant health, it can't be any different than a vegetable bed adjacent to pavement made of asphalt (which is chemically synonomous to bitumen). I have one such bed, growing stuff well, and I haven't keeled over yet. At low temperatures, it's pretty inert stuff.

My experience is limited to window boxes, but here is what I have learned: - Plastic liners do help to slow down the rot as well as retain moisture. They will also provide a barrier between the roots and any chemicals in the treated wood (which retard fungle & plant growth in addition to edible concerns). -Angle brackets for supports are definitely recommended if you want it to last longer. Drainage is necessary of course. To reduce the bottom wood exposure to moisture drill a larger hole (1”) than the plastic liner. All wood rots eventually, even teak, so be prepared for periodically mending. I‘ve been toying with the idea of trying fiber cement composit boards (from remnants). - Soil: Potting mix or leaf fro will be much lighter than topsoil. If using top soil add some peat or composted wood chips to lighten and loosen the soil. Mixing in some Soil Moist granules will help a great deal in reducing the frequency you need to water and makes the plants very happy. I’ve heard that baby diapers do the same thing but have never tried it. i Would also add a slow release fertilizer to store bought top soil. The design looks beautiful and ambitious. I would love to have one on my patio. It would get the strawberries away from the slugs, mice, and chipmunks who eat all of mine. Enjoy!

That’s looking great! Sorry I forgot to link those planters! Here they are: 1. https://www.allmodern.com/decor-pillows/pdp/arzola-2-piece-iron-pot-planter-set-a000507038.html 2. Pinterest, no source listed 3. https://www.allmodern.com/decor-pillows/pdp/harding-ceramic-pot-planter-a000218939.html?piid=184473898 4. https://www.allmodern.com/decor-pillows/pdp/gaskell-short-polymer-planter-box-a000822555.html (Out of stock, but might be available on other sites) Lots of places sell similar MCM planters: Crate and Barrel, Overstock, Wayfair, Target, West Elm, CB2, ect. I really like the pea gravel you chose. :) ETA: Love these: https://www.hairpinlegs.com/collections/furniture/products/bullet-planter?variant=23424592183354 I saw them in this Atomic Ranch article (love that site): https://www.atomic-ranch.com/home-decor/affordable-bullet-planters/