Right hand position… sigh.
For the last few years, I have completely changed my right hand flat picking technique so that I could play with (much) more power. For 40+ years I used to keep my right hand lightly anchored to the top of the bridge when flat-picking single note lines. That made for a bright attack and a lighter touch.
To build a more powerful stroke, I moved my right hand to a place (floating) just short of the end of the fingerboard (near the center of the sound hole). What a difference this made in tone and volume. Notes are much fuller (more piano like) plus the attack of each note is sharper and more energetic. Another advantage with this over the old (bridge as an anchor) technique is that I can go directly from strumming to flat picking without any right hand change of position.
Now to your question. As you have already heard from everyone here, you need to soften your right hand grip on the pick to get a quieter sound. You may have to change your choice of pick gauge for a while as you learn this technique. Different pick materials and gauges sound differently. Experiment and have fun!