a single ring could have less drag, the piston lighter and possibly less compression favoring high rpm and quicker rev building. A two ring piston could have better sealing helping out torque.
What you are trying to imply is torque = midrange or a wider power spread.
We’ll skip over the misconstruesion & run with it.
High speed engines generally run one ring. Above ~8000 rpm it is reckoned that the 2nd ring is just adding drag & not aiding piston to cylinder sealing. Below that the 2nd ring is presumed to be worthwhile.
In the absence of specific tests on this setup, one might presume that an expert rider on high speed tracks & preferably a top end tuned bike would benefit more than trail riding use.
actually I was not trying to imply anything about low rpm= torque. Although the things that help torque tend to favor low rpm, or is it things that favor low rpm tend to help torque? Anyway, things that favor torque; high compression ,less cam overlap, later port timing...... don't really help high rpm.
2 rings helps blow by, one ring, less drag. I noticed that my kids 125, at the time came with single ring pistons, my 250 came with double rings. Double rings therefore help with containing the torque by not allowing blow by. Am I on the right track?:)
Double rings are used in bigger bore bikes that dont turn as many rpms. I dont think two rings increase compression, but will hold compression longer increasing time between rebuilds.