The effect to disable robots is a condition, you can find it under the name of TFCond_MVMBotRadiowave for your plugin.
Code:
TF2_AddCondition(bot, TFCond_MVMBotRadiowave, -1.0);
, in general the condition number is "71", it also works on bots outside of mvm fyi.
To find out if a bot is a giant, or small bot, and/or a boss you have to check those netprops:
"m_bIsMiniBoss" if it's on true the bot is a "giant", if it's on false the bot isn't a "giant" (i.e small bot)
"m_bUseBossHealthBar" if it's on true the bot is a "boss", if it's on false the bot isn't a "boss", however this netprop can't be used to tell if the bot is a giant, you must use "m_bIsMiniBoss".
Finally if that's not enough you can sigcall the function CTFBot::HasTag, and check for the tag "bot_giant" "bot_small" "bot_sentrybuster" "bot_gatebot" to know more infos about a bot.