I only planted cucumbers and spaghetti squash under the trellises. The cucumbers are still going strong having grown up the trellis and about half way down the other side. The spaghetti squash started strong, produced a few gourds, then succumbed to the vine borer. No support was needed for the produce either. Made it really easy for seeing and picking the cucumbers.
I did use the shaded space under the trellis for carrots, beans, and lettuce. That worked out well. I put down some beets, carrots, lettuce, and peas for a fall crop in that same spot.
I did not use the trellis (as I was thinking in the OP) for beans, tomato, flowers, etc. this year. Garden layout went a little different. But the arches do come in handy with nearby tomatoes getting too big for their cages.
Another plus: Birds are always perched on them. So instead of perching in trees a little ways away, they are in the garden more. And hopefully doing their job eating bugs and providing fertilizer.