How many ALGO are currently online, participating in consensus? And by extension, how much ALGO would be required to participate in consensus, at a meaningful rate (e.g. 1-2x/day, at an average of 500,000tx/day)?
You can check live data on ALGO participating in PPoS on Algorand Metrics Decentralization Dashboard or on AlgoExplorer.
I’m not sure I understood the second part of you question but, in my view, each and every ALGO placed at the service of the PPoS and kept properly online through your node is a meaningful decentralization act.
Between 6,000 and 11,000 algos more or less.