We want to set up the external database log. (We have Moodle 3.5) Will this copy the existing logs in the logstore table or will I need to do that manually? After turning on this feature, can we drop the logstore table? The info Moodle provides is pretty light, so sorry for these elemental questions.
This is the page I've found: https://docs.moodle.org/dev/Logging_2#External_database_log_storage_plugin_.28logstore_database.29
QA Testing for Moodle 3.7 has just started, and I noticed today that one of the tests is about using an external database log. Usually the test steps are pretty good about showing you "enough" to get something like that setup and working. I've never performed that test, but it is possibly worth looking at, even though it is for 3.7 and you are on 3.5. Here is a link to the test.
As far as I am aware, it will also stop you viewing logs within Moodle. There's no provision for viewing the contents of 'external' logs.
I would resist the temptation to 'drop' the log table. 'Truncate' it instead. Removing the table completely is unlikely to end well (e.g. during your next upgrade).