Question about how to soundproof a room

I'm thinking of installing soundproofing panels made of mineral wool, with acoustic fabric and wood, and I was wondering if this kind of thing actually works? They come in 8 and 15 cm thicknesses, they're somewhat expensive, and I was thinking of buying about 4 or 6 in total. It's a small room, about 4x5 square meters, but I have no idea where to put them or where they should be strategically placed. I was also thinking of putting bass traps in the corners of the ceiling, but I don't know if that's necessary.

​

​

I'm pretty new to this and it's the first time I've done this kind of things.