About the Blackbeard vs Old Rayleigh debate, difficult to debate properly until the scans are out(especially with the viz), but based on the infos we have thus far, after the conflict, we have
> Rayleigh admitting that he couldn't beat Blackbeard at his current age
> That things were been favorable for them
> Hancock was saved while Coby ended up captured
So whatever off-panel thing that happened leading to Coby's capture had nothing to do with a strength issue on Blackbeard's part. The favorable circumstances mentioned by Rayleigh is the key point here
With that said, obviously despite being old, Rayleigh is still a threat to top tiers