How Do You Practice Vocals Quietly Without Losing Proper Technique?

I’ve seen some singers use a pillow, closet practice, straw phonation, semi-occluded vocal exercises, or a voice dampener/mute-style tool when they need to practice quietly. I came across this type of voice dampener.
Curious if anyone has tried tools like this, and whether they affect breath support, resonance, or vocal placement.

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