On the first point - thunderstorms - I remember reaching the summit of Luinne Bheinn many years ago just as a flash and bang occured. Now I'm not one of those crazy fell runners, you understand, but I was down off the peak at some rate of knots
As with others here it's one of the few things I really don't like in the hills (midges and clegs are the others).
On the secondary point, Tolmount and Tom Buidhe. At the risk of giving away my local, quiet approach - Canness and Caenlochan Glens at the head of Glen Isla give an interesting approach to that whole area from the South.
All the best,
John