Which altcoins are best for small payments in terms of transaction costs and speed?
There are many altcoins viable for small payments right now. For example I use Dogecoin because it's quite stable and it's very cheap compared to others. But I'm not sure such altcoins would be scalable enough to process many many transactions.
I think IOTA is because it is not based on the blockchain and actually as more transactions go by its network, the more speed and less cost we'll have. Too bad IOTA team is working not so well on their project...