1. saving buying power, yes, which is to leverage. but the actually cost might be higher than buying shares directly
2. yes, limits losses during down market. but it's double side sword. delta goes down in the down market, but when market bounces back, you will gain less as well as the delta is lower. the delta control is up to you.
people long leap and short short-term options to arbitrage the IV differences. but there are other ways for leveraging, such as buying futures, buying shares directly