But it doesn’t matter. The reason they take each of the two terms to the fourth power is to give whichever one is even just a little bit larger most of the influence on the final result. I explain how this works in more detail here:
http://forum.worldoftanks.asia/index.php?/topic/42767-the-clan-rating-feature-is-now-available/page__st__20__pid__1041247#entry1041247

I’ve done a quick, back-of-the-envelope analysis of the top 200 clans from the SEA server by dumping them in to a spreadsheet and just graphing it out. I didn’t need to go any further that that; the obviously close correlation between average personal rating of clan members and clan rating, and the obvious lack of correlation for every other figure in the chart, make it clear that the SR*C term dominates to the point where everything else is basically unimportant. You can have a look here (scroll to the right to see the chart):
https://docs.google.com/spreadsheets/d/15GV_WRMyAhEV1veeckt92LrsCm1vnPWIQ1hKmh7ZPRI/edit?usp=sharing

TLDR: You want to make your clan rating higher? Don’t bother playing CW or anything like that. Just start kicking members out of your clan, starting with those with the lowest PR.

PR is stupid in itself
number of tier 10 tanks doesnt really mean much above some number
number of battles lately says sth about activity of players of this clan, so clan with a lot battles played lately is more likely to have 2 or 3 teams ready at the same time.

But eGM is the only thing worth anything there

Is it (unknown coefficient)*(clan’s ELO rating) or something else? Where can we get unknown coefficient if that’s the case?

Those “mCoefficients” are quite important, formulas for them are all very similar, writer/designer of formula wanted to give different importance to things like (ELO rating most, clan wars campaign result second but just little above next things, and then some things like how active players in clan are, how many top tiers the clan has and how many players).

ELO rating is basically changing relative to how much each clan wins (it increases more for underdog or new clan if it’s underdog or new clan winning against good clan or increases slower for good clan, when good elo clan wins against bad elo clan), when it’s two similar clans and one wins it gives it “average” increase in elo (if both clans are equal is looses same as other gains).

It is not same as efficiency/performance, you don’t need performance or efficiency to win, it’s just winning that counts. How you get to it doesn’t matter (it can be cap or some tactical deception etc.).