Is there a way to turn them off on horde night also what would be to easiest way to add these bosses to the snow biome?
Fortunately, both questions are connected to the same file in the mod; entitygroups.xml
Go to Config > entitygroups.xml
1. Turning off Horde Night Custom Zombies.
Go to Line 292
add !-- after the first < so it looks like this <!--append
add -- at the end of line 613 before the final > so it looks like this append-->
This will comment out all of the Horde Night instructions and the game will ignore them.
2. If you are running the Snufkin Custom Zombies Plus the custom zombies are all already set to appear in the Snow Biome. The default entitygroups.xml has a very high spawn rate while the entitygroups_lite_version which is the optional replacement in the main Mod folder (would need to be renamed as per the instructions) is a much lighter version. Default for very established open Worlds and lite for new Worlds where regions aren't unlocked yet. Here are the instructions for the Snow Biome for adding the custom zombies.
<append xpath="/entitygroups/entitygroup[@name='SnowZombies']">
<entity name="ZombieArchon" prob="0.5"/>
<entity name="zombieBanshee" prob="0.5"/>
<entity name="ZombieBomber" prob="0.5"/>
<entity name="zombieCowhead" prob="0.5"/>
<entity name="zombieGeist" prob="0.5"/>
<entity name="zombieMantis" prob="0.5"/>
<entity name="zombieParasite" prob="0.5"/>
<entity name="zombiePsycho" prob="0.5"/>
<entity name="zombieScarecrow" prob="0.5"/>
<entity name="zombieScorcher" prob="0.5"/>
<entity name="zombieSiren" prob="0.5"/>
<entity name="ZombieUndertaker" prob="0.5"/>
<entity name="zombieWendigo" prob="0.5"/>
<entity name="zombieWrestler" prob="0.5"/>
<entity name="HellBear" prob="0.5"/>
<entity name="HellBoar" prob="0.5"/>
<entity name="HellFlyer" prob="0.2"/>
<entity name="HellLion" prob="0.5"/>
<entity name="HellShocker" prob="0.2"/>
<entity name="HellWolf" prob="0.5"/>
<entity name="Mittens" prob="0.5"/>
<entity name="zombieMotorhead" prob="0.5"/>
<entity name="Paindeer" prob="0.5"/>
<entity name="SharkWFLB" prob="0.2"/>