Use the search featured at the top of the screen.
Rigol and Siglent are the market leaders in low cost decent products for hobbyists.
Use the search featured at the top of the screen.We have discussed this same topic many times so there is a lot already here for you to read.
I want to use it to measure noise in various projects,
5. Small hand held or benchtop.Unless you have a specific use case for portable, bench top is the way to go. DO NOT buy a USB based scope. The only exception to that rule is the diligent analog discovery scope but again, that's a different use case.
What wattage ?
In 45 years in electronics, have never needed one.
Use differential measurement 'or' a power cord with the earth ground removed (for that very odd time, use with care!).