Can GRIN do this? Can GRIN compete with VISA and remain decentralized and immutable with a fixed supply and no trust in 3rd parties?
s/fixed supply/predictable supply/Yes, that combined with its privacy is what makes it so exciting. You can probably achieve even greater scaling with BTC+LN, and I consider that
quite likely to be what the economy
actually goes toward, but grin is a very different and interesting alternative approach.
If I'm not mistaken, Grin has a 100 byte kernel baggage for each transaction that stays forever. So it might be more scalable than Bitcoin (an impressive feat considering that it adds a level of privacy as well), but still not Visa-level scalable. I'm not sure how it can be compared to LN's much better scaling.
. Sure it may be able to confirm tons of txs quickly, but if some group of people want to 51% attack, you are fucked. Thats what makes Bitcoin super valuable... most vetted for, most tested, most valuable cryptocurrency with a shit ton of hashing power to prevent bad actors from rewriting the ledger.