This is mine. Absolutely love it. Hassle free and extremely maintenance friendly.
Tank water is gravity fed into a four tier crate trickle tower. Sponges and filter floss in upper layers. Bio balls, more sponges and ceramic rings in lower layers. Finished off with my return pump in the bottom crate.
I'd say i'm slightly overstocked but this system copes with the bio load admirably.
For a sump using mainly plant filtration, usually, much more surface area and footprint is required.
Because plant weight, and numbers, must far outweigh, and/or out number the fish.
I have used barrel sumps in the past, and they worked very well. .
To take advantage of footprint for substrate, and light for plants, I prefer a wide open container like a 125ga/6ft tank for planted sumps.
Every little bit helps, with plants though.
My current 125 gal planted sump/refugium, above.