Important Mechanic Changes

Maximum resistance (poison, magic, fire, etc) are now capped at 75%, and the maximum spell cost reduction from enchantments is 75% also

You can no longer sheathe your weapon at any point during an attack to cancel the attack; you can only sheathe your weapon in a time frame before the attack lands or after a small time frame after the attack strikes. Furthermore, if you do still sheathe your weapon, it won't sheathe, and it will simply "cancel" the attack, similar to how you can cancel your attack with a bow if you press the sheathe button while aiming. 

1. Sheathing or blocking after an attack will now only decrease your recovery time, but the stamina drain will now apply appropriately. 

Lower tier bows can be broken by enemies and you can break enemy bows. Breaking bows can now be done with any 2-handed weapon, but 1-handed weapons requires the first perk in the skill tree

Dual wielding mechanics revised

1. Now attack speed is no longer determined by your left hand weapon

2. Normal dual wield attacks are the average speed of your left and right hand weapon. You can mix and match weapons and it does not matter which hand they are in now

3. Dual wield power attacks are a bit different. The left hand weapon gets 2 hits in, so that weapon should have more of an impact on your overall attack speed, similar to vanilla. Now, your dual wield power attack speed is the average of 2x your left hand weapon speed and 1x your right hand weapon speed, to account for the left weapon's extra hit. This still allows you to mix and match weapons to your liking and not feel penalized

4. Need to rerun nemesis

Slightly lower left and right walking and running speeds so they're not equal to forward movement speeds, but they're higher than backward movement speeds

Sprinting power attack is now tied to weapon speed, and will slow down or speed up depending on weapon type, etc. If using nemesis, re-generate it.

Rune traps and soul gem casting traps have been nerfed so that they are less obscenely powerful and you are less forced to stack MR. Physical traps have also been reduced in power somewhat. Rock traps no no longer deal damage. In thousands of hours I’ve never died to a rock trap once, but enemies heedlessly charge straight into them often instantly killing themselves which is obviously undesirable behavior. Rock traps will be harmless now, which isn’t entirely realistic, but the alternative-- stationary boulders are spheres of annihilation waiting for bandits to wade through them-- is worse.

Damage bashing is a bug in vanilla Skyrim that plays the shield/weapon bash animation but actually does the full damage of your weapon. NPCs can do it, and players can use/abuse this to get very quick, low cost attacks out. For 2h weapons specifically, this significantly breaks the balance by allowing slow weapons to come out extremely quickly for little stamina cost. Now, neither you nor NPCs can use this feature/bug.