I wear shirts every day, with suits.
I buy wool suits because they aren't too hot. Never wear black suits during the day. Grey or blue are better. I have four suits, two blazers (one wool, one cashmere with no lining so cooler).
I have about fifteen shirts. I leave two buttons undone when not wearing tie. Always wear the tails inside trousers - with jeans (if jeans are new and shirt pattern goes with jeans) you might get away with not tucking in.
No rolled sleeves. Best shirt sizes are from 3 Wise Men - the length are ideal for tucking tails, others seem to be too short.
Np black suits in day is due to heat or fashion rules? If unwritten rule is charcoal ok?
Primarily fashion. Charcoal is fine, but not too dark (i.e. not so dark it looks like black).
If you don't wear a jacket, black dress pants are fine (in my opinion) - but a full black suit is for funerals or more formal occasions.