I use a Burdizzo emasculatome. Try to work the calves as early as I can get 'em run up in the chute, but prefer to do 'em before they hit 3 mos of age. Bigger is tougher on me and the calves.
I've always liked the Burdizzo - no bleeding, no chance for infection - and I've not 'missed' a nut in 40+ years of doing 'em.
We implant every steer when we 'clamp' 'em.
I've seen tetanus in both baby calves and big 500-800 lb bulls done with the little green cheerio or the surgical tubing elastrators. Granted, it's small numbers compared to the number that are done that way, but it happens.