I had a little experiment on crit rate and crit damage. Here's the detail.
Crit Rate
Method: I count how many crit attack occur during my conquest play. All the attacks done by generals with +crit chance skill are excluded.
Result: 10 crits and 161 normal attacks. That's 10 out of 171 or 10/171 = 0.05847 = 5.847%
Discussion: Note that when calculate the occurrence of something with low probability, the result usually comes with a large error (one lucky hit has a big impact on low mean). So the crit chance is about 5-6%. But if we consider that ET is more likely to make the number beautiful, I would say the base crit chance is 5% (also same as in EW5).
Crit Damage Bonus
Method: Playing 1861 conquest with GB, I conquered everything and declared war on Iroquois. Using Iroquois as my experiment lab, I attacked newely spawn Iroquois infantries with Green Jackets (this is why I played GB) and recorded the damage. This way, I controlled for atk, def, weapon-to-armor coefficient, morale, and also have sufficiently large enough sample of crit damage.
Result:Crit damage
85 81 74 80 93 84 82 90 90 81 89 77 80 78 84 77 78 85 80 82 89
-> average = 82.81, SD = 5.1, n = 21
Non-crit damage
58 61 51 59 56 56 62 63 59 56 55 59 65 61 57 60 60 59 58 62 65 65 57 58 66 82 56 57 66 57 66 58 60 60 64 58 62 65 65 58 61 60 65 62 63 56 66 61 62 65 61 62 66 56 58 58 59 61 62 59 63 60 60 58 61 65 65 63 56 57 65 60 64 60 78 66 58 61 65 63 63 76 62 65
-> average = 61.42, SD = 4.72, n = 84
Discussion: Crit damage bonus = (82.81 / 61.42) - 1 = 0.3483 = 34.83%. This is in line with the crit damage bonus from EW6:1804 where the crit damage multiplier is 1.35. So I guess ET keeps the same formula in this title as well. One more thing, I got 21 crit out of 105 attacks, that is 20%. So I seems the description of Green Jacket Rifleman's Snipe skill ("When attacking infantry, there is a 25% chance to cause critical hits") is a scam, or I was very unlucky.