based on that 36 page thread this is my prediction for that system:
it looks very nice, those growths in live rock and coralline and coverage signifies a nice active food web and there isn't bad algae in the fine details, its a reef aquarium on its peak bell curve regarding health but also max waste stored, you can see the dark pigmentation in the sand. I would not partially work this tank, the first tank in our whole sand rinse thread is a 120 doing the job 5x over just to show what dedication looks like, you'd have the same job.
Your tank has stratifications, waste locked in zones in that bed that are isolated away due to lack of turnover and this is one reason your rocks aren't bearded with algae
break that stratification for 1/3 the tank, likely to send this reef into full on eutrophication which is plant takeover from upwelling of nutrients, the bed has lots of food and waste that are considered risky. if it didnt, the cross section would be pure white.
that being said, people want the sandbed you have, they don't want the laser clean ones. yours has life, is feeding your whole reef in balance, but you have a motivation now to change course and if you select to do that your options are to attempt a customized run, not part of a pattern, or do what two hundreds tanks have done to make it happens safely.
if that was my tank it would be all new sand if that's what you wanted originally, pre rinsed, or it would be your current sand re rinsed in tap water till clear, then ro, then re used with your reef so it is the white clean version with no pigmentation and associated waste.
the rocks would be cleaned off from the minor accumulations on them, to re open pores and exchanges with the water
sand would get the care focus
It will come back, all of it, over time if you deep clean anyway. When I mentioned above you were at the bell curve of a balanced reef that also implies a downside/nonlinear curve coming
the reef is nearing max storage
when an invasion hits due to X reason it will hit hard and if you try and move rocks to access/and accidentally stir up sand you risk a loss event.
your reef looks sharp, but its aging advanced due to the typical bioloading and feeding we all apply, which is making your reef look really great right now but makes partial removal work truly risky.
literally any animals you remove in the sand will come back in time, from holing up in the rocks.