I'd give it the good quality pellets of the size it can swallow first and foremost. Everything else is not so important and can wait or be given in moderate amounts, or as supplements (if accepted by the fish).
The amount of feed is judged by the stomach. Feed until it is bulging. Wait until flat. Feed again. Very simple, no racking brain.
Overfeeding is bad for any fish and for any RTC but especially for large RTCs, subadults and adults.
It's good to see that the homework is being done. I'd not be the one to discourage you, besides you are not asking about this aspect.
Boswell ponds with a transparent side have come out relatively recently. I've not heard of problems with them but again, I doubt there is good long term data out there. I know a few peers who got them. I think it's a good compromise. Now RTC and channels have sharp spines and I personally would fear they pierce your soft wall pond, so I'd have patches on hand to repair, it's not hard, but if a puncture lands on a seam, the pond is toast.