Unfortunately it doesn't work hostile mobs still spawn at night

What are you referring to by "disable mob greifing". There's no such option anywhere, as far as I know. And why do you expect it to stop hostile mobs from spawning?

Unfortunately it doesn't work hostile mobs still spawn at night

You're contradicting yourself a bit here, because spawning has little to do with griefing. And unless you've changed the default settings in any way then OP&C easily protects your claim from "hostile actions".

So, first things first: Player menu => My player config => Page 6 => "Protect from hostile spawn"; this is turned off by default. So yes, normally hostile mobs will still spawn in your claim. In addition: on page 4 you'll notice that "Protect Players from Mobs" is off by default as well. So... you're also not immune to hostile mob attacks.

However.... check page 6 again: "Override Mob griefing rule": that's on by default. So your claim is protected from griefing.

I've used quite a few claim / protection mods in the past and this is really standard behavior. Also note that if you want this to behave different... then all you have to do is change the settings. By default you should have full access to the rules I've mentioned above as a regular player (except for the griefing rule).

Hope this can help!

@ShelLuser The "Override Mob Griefing Rule" setting is not necessarily a toggle for protection from mob griefing though. The actual protection toggles are "Blocks From Mobs", "Entities From Mobs" etc. This one just inserts an additional check for these protection types when the game checks the mob griefing "game rule". There are other checks that exists regardless of what the option is set to. It's explained in the tooltip. Usually its overridden with a "Blocks From Mobs" check.
And it's completely unrelated to hostile mobs spawning anyway and "disabling" the option in fact removes some protections. So I'm very confused about the situation.