21 by miles.
We looked at a house with a similar plot to 91 and it was incredibly overlooked.
Have these been built yet? Are you able to actually see them? Off the plot, I would go for 21, with clear space at the front that wont be built on, and only 1 house overlooking at the back. Even houses 22 and 20 are angled away, so wouldnt be 'looking' at you. The muddle of parking behind house 22 is effectively 2 gardens away, and you wouldnt have to go anywhere near it yourself. I would put a gate in the fence and path to the front door from the parking area. Then you would use your front door.....although again, the last new builds I looked at had nowhere to put shoes and coats, so using the utility may be to your advantage with that. South east garden - you will still get lots of light, just not late in the evening. The walk into the house is a momentary thing that you will stop noticing. It is a functional time. Time spent in the garden is more recreational and (to me) has higher value and importance.
Plot 91 - has the direct overlooking of 95-98. Then houses 92,93,94 and 89 are all angled towards the garden. So standing in the back garden of plot 91, there will be 8 houses with windows facing you. The garages are single storey, so wont act as a visual barrier. All those houses may also act as shade, depending on how close they are, and those gardens (particularly the 95-98 ones) are not big. If being overlooked is an issue for you then the SW light will be difficult to enjoy. And if there is a risk of building on the other side of the hedge, it will become quite hemmed in.
None of these roads are likely to be adopted, check regarding management costs so you can budget for it. Good luck!