The one with the biggest amount of transactions is 2,945 tx on it, and tx are each 10 minutes. so, taking about seconds i would say:
2954/60=4.92 transactions/second.
2954/60=49.23.... typo?
2945/10/60 is closer to your total.
If we're comparing it with Visa, then Bitcoin is still faster since sending a transaction to mempools only take a second.
Yes, it's at risk of double-spend while unconfirmed but that's also the case with banks transfers which have a way longer reversal/chargeback window
You are right there was a typo, since we have block each 10 minutes that should be involved in the equation as you did.
The comparative with visa is tricky, because bitcoin has a transaction limit/time and vice can process a huge amount of transactions, even if the aren't instant as the bitcoin mempool visa can process millions of transactions each day.
On this article we see how huge is the volume:
VisaNet, the card networks payment processing system, handles an average of 150 million transactions per day and the firm claims it is capable of processing more than 24,000 Visa transactions per second.
Source:
https://blog.unibulmerchantservices.com/processing-24000-visa-transactions-per-second-how-its-done/