I have a lot of mods installed... and ERM (+ all "races") and the mod doesn't work, I mean it's supposedly turned on, but when I give "free game" there are biters (vanilla), but I don't see any other enemies (I ran around the map a bit), and when I turn on ERM - RTS GAME - there are NO enemies (not even biters). the list of mods is really long... or maybe I'm doing something wrong? there is no description of how the mod works specifically, step by step.

The mod defaults to only biters on nauvis. You'll have to to change the "Nauvis enemy" in startup setting if you want other enemies there. There are a lot of other settings in both startup and map tab of mod settings. I suggest you go through them to tune your game before you start the "free game".

Ok, I changed the settings - it works but not completely.

1. There is no pentapods race at all - it is only on the manager's list (ctrl+alt+s) (other races are).

pentapods is not selectable and only appear on gleba. ERM functions don't affect them at all.

ok, thank you. I'm curious how to best diversify the game. Just to make it... interesting.

It's hard to say given you have long list of mods.

Any combat mod will change the balance of it. It may make the mod feel too easy if the weapons are OP.

An overhaul mod may throw the balance off as well. E.g it may slow down weapon research which indirectly increase difficulty. The enemy evolve faster than you can handle with low level weapons.

Given it's your first time. It's probably ideal stick with mostly default difficulty to start and set "nauvis enemy" to the ones you want to try. Then you can tune the difficulty settings in map setting if you find it too easy / hard with your set of mods. You'll have to explore the balance.

If you feel adventurous, you can enable zerg on vulcanus and protoss on fulgora. I don't recommend on first try tho, especially if you enable them on nauvis.