I do large almost total water changes. That's my preferred method.
If someone does 25% and it keeps their parameters in control, and it works for them, great, fantastic, keep working it.
But let me share my experience for WHY I do large water changes.
I started off doing the whole 25-50%. Did fine for months, but over time I noticed my nitrates built up slowly and steadily. I started having a whole slew of problems. I tested my nitrates--160ppm+! But I had just done my water change, how did that happen?
It slowly built up because what nitrates were left in my tank after the water change were added upon every so slightly by the next water change. Over the coarse of months it got that bad despite vacuuming and water changes and filter cleaning and plants.
What stopped it?
Performing near total water changes.
My nitrates now range 5-20, increasing to 20 by time my next water change is due.
I stay consistent with my water changes and my fish are happier and healthier with the larger changes compared to my previous routine of just 25-50% weekly.
Plus with fry you need to do daily changes as well. If you can do total changes with fry without ill effect, adult fish can handle the same regiment too.
Thats MY reason for large water changes. I dont expect other people to do the same thing. Different methods work for different people.
But the fact of the matter stands that large water changes, as long as theyre routine, dont harm fish.
As for dechlorinator, I dose the tank amount when I refill. Since I dechlorinate before filling (I use a hose straight from the tap to the tank, no buckets first)