I use egg crate lighting diffusers they use in officer building, these run about 10$ for 4'x2' sheets.

These can be snipped to size for many projects.
Needle point sewing plastic also works very well for smaller projects.

As far as sumps go, I think many folks use this idea with open cell sponge.
I have foam blocks in all my sumps. Like many, I've not noted any filter differences between slow and high flow rates for some rather obvious reasoning.
You want about 30-60 open cells per square inch.

Some places sell the foam blocks etc in large sheets etc(On line, LFS's hobby and craft places etc).

As the foam gets clogged with mulm/detritus, the flow rates slow down in most areas and you get some pocketing / uneven flow. The sites of low flow yield the slower flows that are better at filtration.

When folks discuss filtration, and biological systems, clogging is a huge issue, Bio balls have less surface area, but they do not clog for years.

There is a trade off.

Bioflims and organic materials clog and foul filter media, you have to keep up on it and clean it every so often to have it work at top levels of performance.
The issues and idea here are very old and it sounds a lot like a new name and an old idea.

Regards,
Tom Barr