The difference between mempool "bytes" and "usage" getmempoolinfo returns bytes and usage. Currently, the value I have for bytes is 1316363 and the value I have for usage is 4826112.

I'm assuming that bytes is how much space these transactions would require if they were to be included in a block while usage is the size they are currently taking on my computer. That would imply that the transactions get compressed somehow (or some nonessential info gets stripped away) before they're included in a block. Is that correct or am I way off?
From the documentation: 

  "bytes": xxxxx,              (numeric) Sum of all virtual transaction sizes as defined in BIP 141. Differs from actual serialized size because witness data is discounted
  "usage": xxxxx,              (numeric) Total memory usage for the mempool


bytes is the size as calculated as vBytes as would be considered for inclusion in a block, usage is the logical size in actual bytes that are consuming memory.