We're talking about the user-visible behavior. You argued that because Cloudflare's CDN has an obscene amount of bandwidth, R2 will be able to saturate user bandwidth; that doesn't follow, hence my counterpoint that it could be bottlenecked on storage rather than network. The question at hand is what performance R2 offers, and that hasn't been answered.
There are any number of ways they could implement R2 that would allow it to run at full wire speed, but S3 doesn't run at full wire speed by default (unless you make many parallel requests) and I'd be surprised if R2 does.
n = 1 aside.
I have some large files stored in R2 and a 50Gbps interface to the world.
curl to Linode's speed test is ~200MB/sec.
curl to R2 is also ~200MB/sec.
I'm only getting 1Gbps but given that Linode's speed is pretty much the same I would think the bottleneck is somewhere else. Dually, R2 gives you at least 1Gbps.