Golems, Minotaurs, and Minos are good both in terms of appearance and stats, as well as their survivability)) They are good defenders, and they also form a decent core at the beginning)... in principle, you can also include bears and orcs here... although the latter are weak without Blood Fury) and bears are good attackers)
Cerberus is good thanks to its speed and attack)) after that, it's basically useless... it looks ugly
Elves... everyone knows that) archers, two shots, etc.)
Ghosts, even though they sometimes annoy with their transparency)) but if they get hit, that's it... and their attack isn't very good)... this is more of a distracting unit
P.S. Level 3 is the most difficult choice, because almost all of them are good)