Which teeth whitening procedure is best?

When looking at people, those with white and neat teeth also make viewers feel refreshed, so these days I prefer and am interested in teeth whitening~ A friend who is aspiring to be a model did it, and it was okay after the first session, but from the second session, she experienced tooth sensitivity, so I was told to carefully examine the procedure method.

I have occasionally used the peel-off whitening strips sold at Olive Young a few times, but they are almost single-use, so I think I should consider their cost-effectiveness.

I'm seeking advice from anyone who has tried teeth whitening just in case!!