I would love to receive some advice on choosing the right size and shape for vines. For example, for Vigna caracalla, it's supposed to grow 15-20', but how wide? Should I get a long trellis or a wide trellis? Is it a matter of pruning to control/shape it? I'd like to grow different vines against a wall of 25' long and 15' tall. Not sure how many vines I can fit. So for I got Vigna caracalla, Honeysuckle 'Golden Flame', and Ampelopsis brevipedunculata 'Elegans', and Passionflora 'Pink Lady'. They are all about 15' long.
Thanks in advance for your advice!
Size of trellis
You have chosen some big vines. I like to recommend using cattle panels, found in the concrete section at Home Depot. Against a wall, the panel would soon be covered in vines, so not seen. The Vigna will be swollowed up by the other vines you've planted - I'd find a place for it, where it doesn't have to compete with its much bigger cousins.