Basically, Yes. Both of these procedures change the shapes of your teeth by gently removing a little of the enamel and then polishing those areas. This can result in a dramatic improvement in your smile. Over a lifetime, this enamel is going to be lost to "normal" wear & tear anyway, slowly over the years, so removing it a bit ahead of schedule does no real harm. Just be conservative and take only what you need.
Yes, a little is ok. Dentist remove and frequently replace enamel. If the enamel removal leads to better function, as well as cosmetics, it can be very valuable not to replace it. Most patients have thick enamel covering their teeth but throughout life, wear it away. Tooth grinding at night, brushing with whitening toothpaste with abrasive grit cause far more loss for most patients. Replacement is commonly necessary.
Conservative. Usually this is a very conservative treatment- not a lot of tooth structure filed down, usually no novocaine needed.