We are a Dell shop in the same situation. Some of my servers were replaced with BOSS cards and run ESXi 7.0.2E
My older FC 430 cluster cannot get rid of the SD cards and we kept it on 7.0.1E
7.0.2 will destroy your SD cards (even the so called patched C build).
You can mix servers in a cluster on different editions, while not best practice, it is 100% supported
I would steer clear of ESXi 7.0.3 , they have butchered the interface and it seems to have a lot of problems (so many that they actually pulled earlier versions of 7.0.3 from the downloads !!), not to mention some backup vendors still do not support 7.03
My opinion :
vCenter 7.0.2 latest build
BOSS Cards = 7.0.2 latest build
SD Cards = 7.0.1 latest build