besides royals wat are some other plecos that need wood?for instance do a sailfin and blue phantom need driftwood?
I don't know about the phantoms, but sailfins don't need wood, although it is a welcome addition to their diet (it helps with digestion).
This is correct, for the both of them. It's not vital but advisable.
And as for specific wood eaters, afaik all Panaque/Panaqolus and some Hypostomus/Cochliodon. These are the one with teeth specifically 'designed' to gouge wood. And theres probably another odd one or two that do it as well. But be aware that wood 'eaters' don't eat the wood per se, they consume it as by product of their feeding strategy.