I'm surprised you don't list the most natural and proven methods
-DSB,
- macro algae, and
-a higher system density of live rock to provide safe harbor for bacteria and other bio diverse critters to consume and breakdown the Po4
I had a 300g+ system that had a heavy bio load and never had a Po4 or No3 issue.
I now run a 110g and heavy feed daily (pellets, cyclopsezes and mysis) and never have had a p04 or No3 issue.
The way I see it there are really 3 methods with several sub methods
1) Natural - provide enough bio diversity in the form of space and diversity to consume excess Po4 (live rock, sand and macro algae)
2) Supplement bacteria cultures that otherwise can't reach enough population to consume Po4 (carbon dosing and bio pellets)
3) Mechanical removal (GFO and others)