I just noticed in this snapshot and not previous ones that the destroy block lag that you get right after world creation is continuing throughout the game and restarts of the client. I upped the RAM to 3GB and it still lags. It also seems to be loading more chunks but I reduced my view distance too and no improvement.
MC-124732
Destroy Block Lag
Resolved
Duplicate
0
Adam Jordan
(Unassigned)
Unconfirmed
Minecraft 18w05a
Retrieved
Actually this may be my computer issue. Seems when I have a second user logged into Win10 that switching back to my main account causes a slowdown. I loaded the same world back up with just my main Win10 account logged in and there was no lag. Prior to 1.12 I was playing with both Win10 accounts logged in and never noticed this issue but at this point I don't think your time is best spent on this issue.