Going back to some of the other questions in your opening post...
"Rotational" grazing means, to me at least, grazing more than one species in a sequence, so that each species eats and nullifies the worm eggs which would affect the other(s). Done right, it can be extremely effective for worm control.
But rotating one species through a number of paddocks is still a good idea. Sheep like fresh ground, so subdividing and moving them on is a good plan for their wellbeing as well as for helping with worm control.
Electric fence, if the right type, set up correctly and maintained correctly, can work well with sheep - but it doesn't always work with very young lambs. (Wool is a good insulator, and lambs have such a tiny point of contact with the ground that they don't seem to get much of a shock until they're bigger.) So if and when you breed, personally I would lamb in a separate stock-fenced area, and introduce electric once the lambs are getting bigger.
My experience is that the more primitive (and wily) the sheep, the harder it is to keep them where you would like them. I'd expect Soay to be hard work with electric, to jump it, to know when the charge is low and they can breach it, and for it to not affect their lambs at all. And they're horned, so you won't be able to use the squared mesh style.
If you decide on a configuration where you'll be rolling up and redeploying the electricity carrier, I'd say go for wire over rope or tape. The fine filaments in rope and tape break down the more you roll it up, and you'll need to walk the entire length regularly checking
all the strands individually for loss of transmission.
In terms of numbers, it depends massively on your ground, but the rule of thumb for decent/good ground is 5 commercial type sheep per acre, more - 7 or 8 probably - for the small primitive types.
When you start breeding, the numbers grow frighteningly fast, especially at the outset when you inevitably want to keep
all the pretty little girls
, so don't go mad with the numbers of breeding ewes you buy in at the outset.
Some of the primitives are browsers as much or more than grazers, and they won't necessarily keep the grass short and tidy (unless you give them no option by stocking densely), so tbh, if your aim is easy to keep lawnmowers and lamb boxes to sell, Soay is probably about the last breed we'd recommend, and you might do better with a more Downs-type sheep.
And can you talk some more about the shearing/flystrike thing, because there really aren't very many choices of self-shedding sheep (and only Easycare is likely to meet that list of requirements IMO), but we can give you a huge list of suitable breeds and types if you can live with woolly sheep! lol.
Whereabouts are you? (Cos it'll help us know what sheep are likely to be around for you.)