Bad to run 120rms to 100rms speakers

you dont have to use all of the amps power, better to have more on tap than not enough....can always tune it down. and prolly an actual 50 rms to those will probably be louder than you can tolerate....but with more power comes dynamics....just set gains very conservative

you can run 500 watts to a 50 watt speaker, if youre careful

set the amp gain right... https://jlaudio.zendesk.com/hc/en-us/articles/204374120-Amplifier-Level-Setting-Guide

heres the tones... https://www.realmofexcursion.com/downloads.htm

Actually most speakers / subwoofer like reserved clean power and you can certainly run even 75% more power but it also comes down to your music preference and loudness. if you are cranking the volume most time to satisfy your listening pleasure knowing you are driving your speakers into distortion, then you are cutting the life of your gear and its only a matter of time they will fail you.  20RMS More and your speakers will not notice the difference.  Remember with every double of power, you get that 3decibels so if you want volume, then you have two options:

• get a more powerful component speakers;
  
• get two sets of component speakers;
  

Hope the information is helpful to you mate!

BTW,  I am running 444rms RMS each to a pair of Alpine SWA-12S4.  They are rated at 250rms so I have lots of head room and I make sure I don't drive them to distortion and since I have two, they are efficient enough to fill the car with bass even at moderate listening levels.  Its always good to have more reserve power then less, as its the clipping from amplifiers that drive speakers to distortion resulting to speaker damage. Just keep tab of the distortion and you should be fine mate!

You can limit the amps rms capability when you set the gain properly. This is the most correct way of doing it and should be able to listen to your stereo all day all night w/o issues. Also don't worry about "max" power....that's the same thing as peak power. A few second "burst" of power that speaker can take before it's toast. RMS (Root Mean Squared) is the most important thing to look for. It's for continuously daily listening. Lastly, the square root of 100 is 10...would be the number on your DMM to tune the amp with, setting gain properly.