How many transactions per second could the Grin network do right now? What plans are there to increase that if needed?
~1.5 MB max block size, with a block per minute. Transactions are much larger than Bitcoin, though. So about 14 tps right now.
Bitcoin's scaling is limited to a large degree by the need for historical blocks to be widely available. Grin on the other hand can mostly forget its history, so its full nodes only need to store/process
live transactions, and grin can safely increase its max block size linearly with worldwide Internet speeds and/or CPU speeds.
Many altcoins just increase their max block size and hope for the best, but if any of these altcoins were actually widely used, this would cause severe centralization at best or total system failures at worst. It's like putting a bigger "max capacity" sign on an airplane. Some altcoins have ways of cutting out old history, but although there are theoretically some not-too-bad ways of doing this, usually altcoins do it in really centralized/stupid ways (eg. checkpoints, or ETH "full nodes" just not bothering to verify anything by default), and even in the best case it results in a loss of functionality and security. grin is the first coin with a reasonable, decentralized, and secure way of dropping historical data.