i THINK i beat this game on Kong before. the commanders are quite useless and weak after the first few battles, unlike previous games and the MMO edition. best graphics in the series but more simplistic in mechanics. should have added some NG medals.
just like in EW4, you gonna need those goblins and 1 "white tiger". w-tigers "evolved" into a giant white wolf in this one. some levels require faster melee units to beat the boss or at least delay them while your mages and elves shoot it down.
note: that the Angel boss is immune to magic. the Fortress boss is immune to pierce attacks, but you don't wanna bring archers anyway because its attack is long range and too fast for your ranged units to survive even 1 hit. the final bonus level with a super Amazon is surprisingly easy once you levelled up your titan unit. that amazon can heal with each attack so you will probably need the Rage spell to ensure you damage it more than it heals.
spoilers/ text walkthrough i found for the tougher levels: rollingskyblog.wordpress.com/2017/06/02/epic-war-5-walkthrough/