In inguinal hernia repair surgery if some of the cremasteric fibres/muscles gets excised will it cause reduced/absent cremasteric reflexes that side?

Possibly: If all the fibers were to get cut or removed you would not have a cremasteric reflex. Sometimes the muscle may heal back together and i would guess the reflex may return or strengthen.

No: Usually the muscles get split and not excised, so should not change much!

No: Why are you worried about the cremasteric response ? The muscle is not cut out during surgery it is spread apart to expose the sac and cord structures