High hairline with a broad curved & bony forehead. Is the best surgical solution hair lowering or excess bone reduction? (Photo)

You need an examination of your scalp and understanding of risks with realistic goals/expectations.

One risk is that forehead reduction surgery leaves a scar on the hairline no matter which surgeon or type of surgery performed. If you have genetic balding this scar will be highly visible years down the line.  

Hair transplant surgery may be an option for a forehead reduction. Hair transplant surgery does not leave a scar on the forehead. Like all cosmetic surgery, how "natural" this may look depend on the artistry of the surgeon. Hair transplant surgery limitation is that the results are not immediate and the growth will not be as "full" as a forehead reduction surgery.

The best hairline lowering procedure for men is done through hair transplantation. That is because men's hairline usually continues to recede. The number of sessions
varies by the thickness of the hair. With finer hair, it often takes two
sessions. The time to see the impact of a hairline lowering hair transplant
procedure is 7-8 months and if a second session is required, it will take another
7-8 months to wait for full growth. See web-references below show hundreds of men with problems like yours.