what is the fastest way to place more blocks? (e.g. for colormatch or worldfixer) i think there is faster way than $level->setBlock()
setBlock() would be the fastest. Other method is by sending packets. That might he faster but I'm not sure.
First: do you want to save the changes, or at least let the server know about the changes (to make server know that there is a block or a hole)? Yes: use setBlockIdAt(), which does not send the changes to the players. Then unload the changed chunks for the players so that the chunks will be sent to them again No: use sendBlocks() to send the changes to the players without modifying values server side.
These cool functions didn't exist when I initially wrote it I am now using setBlock() in my rewrite, but I do it gradually, so lag isn't a concern as long as setBlock() rate is low.