In the setting below, if "enabled" is set to "false", will the the attack cooldown will still be active/enabled,? I know this is basic stuff, but I'm making changes to these settings and using /ocm reload, but I'm not seeing the difference. Just wondering if you could clarify how this is supposed to work since we are "enabling" a "disable".

disable-attack-cooldown:
enabled: false
worlds: []
generic-attack-speed: 4

More specifically, what settings do you recommend here to achieve the closest mechanics to 1.8.9 pvp?

After looking at your module class, I understand the settings, but I'm having trouble seeing the changes take affect. Does a /ocm reload apply changes immediately for a 1.14.4 server build?

Yes, it does.

what settings do you recommend here to achieve the closest mechanics to 1.8.9 pvp?

The default settings should be the closest to 1.8.9 PVP. However, for a full 1.8.9 experience, you may wish to also enable disable-player-collisions, no-lapis-enchantments, and disable-elytra. (you can also turn on disable-bow-boost and chorus-fruit.prevent-eating, but these have very little impact on the game)