I like that trellis, especially the wire vice, as I always found it a pain to try to maintain tension on wire systems. Twisting the support wires and securing the rebar also looks like a good idea. I used to just loop the wire through and tie it to large rocks, then try to nudge the boulder a bit further to get enough tension. Not a method I recommend.
If they are saying 16-20 ft apart, I think the following is about as small as I’d want to go:

This gives each female vine 15 feet and the male in the middle 10 feet (and you can prune it harder if needed). To get a full 50 feet, you’d need another post, which isn’t a horrible idea, but you can probably get by without it if space and/or materials are limited.
I feel like 3 would be plenty. Kiwi are pretty vigorous and the one thing you want to avoid with them is getting them tangled up on themselves. I’ve spent way way too much time trying to sort things out. Having 3 wires further apart seems a lot easier to maintain, rather than trying to fit 5 main cordon in there. This assumes that you are going to have the vine grow like this (trellis in black, vine in blue):

I shudder to think about trying to keep the side branches from jumping from one wire to another if they are that close together. I know that it would eventually be a sold mass. And once it is a solid mass, it gets hard to prune the water spouts that shoot up. And once that happens, it the whole fruiting area moves higher and higher. Eventually, it gets even harder to reach and less likely to get pruned, meanwhile any fruit is 8+ feet high. At that point, I spent a long time with hedge trimmers, swinging it wildly back and forth (quite a workout). Now that I just relived that nightmare, I could even be convinced to go with 2 wires instead of 3
Semi-kidding…You can probably make it work with 3. Or maybe even 5 if you are way more attentive than me.
But, I guess it could also depend on how well kiwi grow in your area. While they are super vigorous for me, I’ve heard that they have trouble surviving from growers in places like Kansas. Keep in mind that 3 wires * 15 feet is still 45 feet of trellis space (plus a bit from the width of the T).
Male in the center makes sense to me- might as well make the pollinator central. You can also let it take more trellis space initially, then prune it back once it is more mature and consistently flowering.
The trellis in the video is 6’ tall, which is reasonable. I wouldn’t mind a bit higher, as I wouldn’t hit my head as much. At the same time, higher could make pruning difficult, as you need to regularly prune off any vertical growth. And by regularly, I mean whenever you walk by it. If you need to go get a ladder, that is enough of a barrier that it will make it less regular than it should be, so keeping it low enough to be within easy reach is important. I wouldn’t go any more than 6.5’ myself (speaking as someone who is ~6’ tall), as you may need to reach through the vine to get to the part you want to cut.
Where did you find a purple variety? I’ve been going back and forth on whether to transplant any hardy kiwi to the new yard. If I could find a purple variety, it would probably give me the push to move 1 cordifolia and 1 male. And maybe do a trellis like you showed above.
I know I’m not moving all of them. I’ve already told one of the guys at the farmers market that I’ve got some vines for him, if he wants to dig.
None that I know of. The only vine which was a bit lower in vigor was Issai, a female. Though, since it is partially self-fertile, maybe there are a few male flowers in there. I wouldn’t rely on that possibility though.