I don't think #1 and #34 would be improved with your hand drawn design. They have a very geometric rectilinear "vibe" that appeals. Well, too me anyway.
But then that takes away my little personal touch

However, I think #47 might have issues with different shirt sizes. I assume there is a single size design which is applied to different sized shirts, so a large shirt (me unfortunately) might not look quite as good as the design completely filling a small shirt.
Good question. I don't know if they scale the design slightly for different size shirts. I would have thought so

It is those traces running off to the periphery and the Vout running all the way up to the sleeve.
Yes, I would get the design smaller so Vout doesn't run off the side.
I slightly prefer #47 to #37 but think #37 is a better fitting design for a shirtfront. Is it more costly to have more colours?
I don't think so, will have to check.
In any case I am amazed at how well this process has seemed to work. Perhaps that is partly because designs I like have filtered up. I wish I could pick horses in the Melbourne Cup as well. 
I was sceptical at first too as some very ordinary designs rolled in, but now I'd be happy with at least 3 of them almost as-is.
The alternative was to try the woman who did our Amp Hour t-shirt. But that was a one-shot deal, so I liked the idea of getting many different ones to pick from.