On the subject of hotspots, most lenses have hotspots at their narrowest apertures and most do not have hotspots wide open. When hotspots show up - and how strong they are - varies by lens. You can test your lens by shooting some test frames at various apertures against a clear blue sky about 120 degrees opposite the sun.
The Nikon 28-70 is pretty good at avoiding hotspots. The Nikon 24-70 is much more mixed - my copy hotspots at f/6.3 and narrower. There are lots of 50mm primes available and some hotspot badly while others do not.
Generally f/8 and wider open is a good compromise on avoiding hotspots and creating some latitude with focus.
Be careful to not let direct sun hit the front of your lens - and where possible avoid it reflecting off the lens hood as well. IR is quite prone to flare, hotspots, and other artifacts of stray light.