I have hatchery birds of these types. (Well, the "Delaware" is actually a changeling Leghorn.) None of the other 3 seemed particularly bothered by the heat (very high 90s). The SLWyandotte started laying first (17+ weeks). Still waiting on the rest. The BR has the best temperament by far (dominant, but never mean). My sample size is tiny
, but you can add it to the collective info.
If you can find good heritage strains, they will probably look and perform differently than mine. Of course the hatchery types are easier to replace every couple of years.
Edited to add: Just saw your later post. Love the white columbian look also. Keep in mind though, that white birds are easier targets for predators.