Which altcoins are best for small payments in terms of transaction costs and speed?
I think right now raiblocks is the best in term of cost and speed, only a matter of time before people start using this more. Litecoin is also very good for sending small payments and there's quite a lot of places that accept litecoin alongside with bitcoin. I only use that two if i can because it's always cheaper and faster rather than using bitcoin or ethereum (especially when the network is clogged).
Raiblock is no doubt with that because it has high potential and high community.
Litecoin also good choice to send small payment but talking about the price, litecoin is very slow moving