I see this quite often, people searching for countermeasures they need to enable, people searching for more magic tips...
If there were useful things that had a good chance of dealing with bots and not killing innocent users, then we would already have integrated them in UnrealIRCd or they would be in development. Similarly, they would be enabled by default or mentioned in the example configuration file, like all our anti flood and anti bot countermeasures.
After all, why would keep good things out or disabled? Why would we keep things secret or left up to the admin to enable, if they are a great countermeasure?

It almost seems like people are surprised that we have so many anti flood features enabled by default. Indeed, most of them are documented at
https://www.unrealircd.org/docs/Anti-flood_features. The only great feature that isn't enabled by default, because it requires channel-specific settings is channel mode +f, so I suggest you look at that (again documented at that page).
To sortof "answer" your last "question". When your network is attacked by multiple bots, that is: a sudden spike in connections per minute, then
https://www.unrealircd.org/docs/Connthrottle will kick in.