Cattle panel would be much more solid. That’s what we build hoop runs out of for our chickens - both cattle panel and this 2x4 fence - 1/2” mechanical mesh to fend off the snakes.
If you don’t reinforce it, of course it’s flimsy. It needs to be reinforced to be a table if it’s expected to hold a million pounds of plants.
Hardware cloth would be an option but needs support. Use treated wood in your construction. You will probably have to replace the wood any kind of water.
That welded wire fencing isn't very strong and the welds break pretty easily. You would be better off using horse panels (they are the same 2x4" spacing but made with much heavier wire and better welds) or cattle panels (similar to the horse panels but with larger holes).
Yes. I used 2x4’s (3’x8’) as the frame and stapled that to frame. I found I needed a support in the middle. I send wire shelves used in closets on the walls and those p/down pulleys for hanging pots from the ceiling.