OK I got a support response, and these steps seem to have largely solved the lag issue. I'll continue to monitor.
Select Tools > Options >Syncronization
Set the Synchronization setting to 5 Minutes
Select the Note in the option window
Scroll down and select Show Advanced Options
Uncheck Show Context
Then, if that doesn't fix it, try this:
Rreinstalling the local copy of your notes. This is called a database rebuild.
To rebuild your Evernote for Windows database, follow these steps:
If you don't have any unsynchronized notes, and you do not have Local notebooks, please skip to "Move your existing Evernote database." If you do have unsynchronized notes or local notebooks, follow these steps to export that content:
Select all unsynced notes, or each local notebook, then right-click and select Export Notes…
Choose 'Export as a file in ENEX format (.enex)', then click Export
Detailed instructions here
Move your existing Evernote database:
Open Evernote for Windows
Select File > Sign out… from the menu bar
Select Evernote > Options > General > Open Database folder
Move the [username].exb file to your desktop
Open Evernote and log in to your Evernote account
Evernote will download all of your synced notes from the servers and create a new database on your computer. You can then import any exported notes by selecting File > Import from the menu bar.