I doubt if there's an "ideal" design for a stitching pony, like many things they can be made to suit specific needs. As a general purpose one I think yours looks about right, with the design of the jaws allowing for holding different shapes. Mine is roughly the size of yours and I've made several western-style holsters on it (they can be tricky to clamp) and associated gunbelts. For the gunbelts longer jaws would have been nice but then they might have been a nuisance on other projects.
As for clamping pressure, that will vary depending on the project, which is why the adjustable locking lever is good, just tighten or loosen as required. And when stitching long runs the thread WILL get caught on the locking lever!!!!