Regarding speed, it would be more accurate to say "if you move before your opponent," and for this, you don't always need Phoenixes – because a level 3 Dragonfly on its home territory will only be slower than upgraded level 7 monsters from 5 different castles, and you still need to survive until then...
Справочник по НоММ-4 http://handbookhmm.ru/pamyatka-dlya-heroes-iv.html
Памятка по НоММ-3 http://handbookhmm.ru/pamyatka-dlya-homm-iii.html
и HotA http://handbookhmm.ru/vyishla-obnovlennaya-pamyatka-dlya-homm-iii-hota.html