I discussed this with my mechanic. He said that there should be no issues with alignment simply because it’s a standard Shimano brake caliper using standard rotor. So using another Shimano rotor should make no difference in alignment. Makes sense to me.

In terms of cooling as he explained it’s not due to aerodynamic properties but the internal sandwich structure steel and aluminum. Aluminum dissipate heat better.

In terms of disk structure it’s an interesting point glye made. RT86 rotor also looks much stiffer to me compared to ultra light design. However there will be much less rotational forces for same braking effort considering 18 inch wheels and it should probably be fine. At least my mechanic said it will be and warranty on the rotor will hold.