All three methods you mentioned will kill the moss wherever the solution touches. I find boiling water the least harmful to surrounding plants; use a teakettle-the spout helps control the pour. You might like to try sprinkling lime OR fertilizer [such as 10-10-10] on the pavers; undiluted both will kill the moss, however, rain will dilute and affect the surrounding plants -- don't use lime if you have acid-loving plants nearby. After the moss dies, use a stiff scrub-brush or broom to sweep the dead moss off the pavers -- even dead, it will make the pavers slippery when wet.