Whippet- neuter and food advice by vet- please help

[Charliee]

Just got back from my vet who told me NOT to neuter my male Whippet as this will reduce his Whippet/athletic characteristics. He also said because they are such a loyal even temperd breed that personality wise there would be no advantages. (FYI He's only a family pet, no shows or lure coursing in his future.) The breeder we got the puppy from did say he has never needed to neuter any of his male dogs, just females.
I was also advised by the vet to start changing him over to adult food after 4 months to limit any tendon problems associated with quick bone growth caused by the puppy food. ?????

I'm a 1st time dog owner and this advise seems to go against everything I've read to date. Does this make sense to any other Whipppet owners out there?

Thanks in advance!