"Might vs. Magic"

I don't understand, please specify by which parameter (damage, attack, defense, health) Naga are weaker than other 6th-level units.

Did I claim that somewhere ?

Upgrading Naga to Queens is task #1 in the 2nd week.

Who would argue ... only it's not always the case. And it's much easier to buy some horses on 121 and go-go break everything even without an upgrade.

Regarding unit speed, doesn't anyone take Air and Haste for Tower?

Air and haste are not a prerogative of Tower, other castles have them too, so it doesn't change the balance of power. But while many other castles can do without it, Tower finds it harder to manage. That is, when Castle-Rampart-Dungeon shine with their strike stack, Tower is forced to haste its stacks one by one.

Take the Griffin Conservatory - even on native terrain we have a speed parity for griffins, gremlins, naga, iron golems. But on non-native terrain, griffins move earlier. You need to carefully calculate turn order, and again use haste.

Yesterday, for instance, I played Tower vs Tower with Matroskin, in battles I was mostly busy hasting either gremlins or naga (there was no money at first, then no chain for their upgrade). Given that mana is not infinite, and you also want to use other spells.

but the respawn is richer than average

Where did you get that information from? :)