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Looks like touring wheels?
For touring I would fit as many spokes as possible at the rear... firstly because the wheel will be stronger and last longer given equal everything else, but more importantly as if you had to break a spoke in the middle of nowhere for any reason, you would be able to cycle to nearest LBS, thing which realistically you might or might not be able to do with a 28 H and certainly not with anything lower.
For touring with load, 36 would be my choice.
The front is less important, in that it's less likely to cause you grief, so if you have a 28, that will do, although I would still go for 32 or 36 if travelling long distance.
No, but I nearly bought a shutter precision dynamo in 28 holes from Germany for cheap.