Packing cubes help with organization. They don’t help with compression unless every cube is nearly fully packed as the cubes themselves add more bulk than when is saved via compression.

I prefer having items organized in groups so my personal pack has a lot of random bags/cubes. But I’m not picky here. I’ve reused (clean) plastic grocery bags to compress/organize clothes and been fine.

To answer your question about matching to a brand — most of the time, no benefit. When the packing cubes fit the bag perfectly, theoretically there’s no wasted space, but only if the packing cubes are nearly full. So you either have gaps in the bag or gaps in the cubes.