TSC has the same Behlen panels in your first post in red, that are heavy duty.
Those work for horses, other than the round tops on the ends, that could be a problem if a horse hangs a leg in that gap.
Happens very, very rarely, but it does happen.
Depends on how risk adverse you may be.
We have Powder River panels between horses, have had for years.
The old ones had curved tops, we have them around the outside arena, the new ones are square and are in the horse pens and runs.
The old gates still have rounded corners, the new ones square ones.
We have not had any of those bent or damaged in any way, but never say never: