Yes, they do. A block size determines what is the maximum amount of information a block from the blockchain can hold before a new block needs to be created. It doesn't mean blockchains wait for blocks to be filled until they produce new blocks, they usually produce them regularly (Hive produces them every 3 seconds), and it doesn't matter how filled the previous blocks are. But when blocks get regularly filled, then usually the discussion of increasing the block size arises, as a way to further scale a blockchain. Before that, it's not necessary to increase the block size, even if you can.
Yes, they do. A block size determines what is the maximum amount of information a block from the blockchain can hold before a new block needs to be created. It doesn't mean blockchains wait for blocks to be filled until they produce new blocks, they usually produce them regularly (Hive produces them every 3 seconds), and it doesn't matter how filled the previous blocks are. But when blocks get regularly filled, then usually the discussion of increasing the block size arises, as a way to further scale a blockchain. Before that, it's not necessary to increase the block size, even if you can.