Patchy always has done a fine job on my gardens, but the downside is he doesn't always come out and go to work every day. On the other hand, the garden can survive a day without care. Really your call.
Gardeners have some glitches, I've read, if your plants are spread rather than all together in one spot. No idea if this is true, I have not seen the glitch in my game despite having one house with flower beds in front and a garden along the side plus some potted plants on the front porch. Even with that spread, the total distance between the nearest plant in each area was not too much, so maybe that's why I never saw the glitch I read about.
Nannies not leaving...yah, that's definitely what happens in my game too. Last time I hired a nanny I forgot to dismiss them and sent all my sims off to bed. Only realized they were still around when I started panning around the house (and changing floors) to find what non-active sim was preventing super-speed from kicking in. LOL I don't recall him charging all that much when I finally found him and dismissed him though.