What does it mean to name your son Feng Haoyu?

Haoyu means the bright sun shining on your head. very good!

If the character Hao does not refer to seniority, can it be changed to Feng Yuhao?

Because from a rhythmic perspective, Feng Haoyu is relatively plain; while Feng Yuhao’s pronunciation has a sense of yin and yang. Just a personal suggestion for reference!