The enemy projectiles in Skyrim are ridiculously fast. You cannot dodge or block them by reaction time, all you can do is to sidestep and juke the enemies to miss. While in most modern action combat game, enemy range attacks can be dodged, which rewards skillful gameplay instead of stat-check.

Action Based Projectiles (ABP) is inspired by (SGC) Dodgeable Arrows Spells and Shouts. But with tweaked speed to fit my playstyle more. (Distar's setting is too slow for my taste. ) I tested several numbers and the result below are best-fit for me, you can change them if you prefer different speed.

With True Directional Movement's lock-on and predictive projectile aim support, you no longer need to worry about slow projectile speed causing missed attack.

Below you can see some of the speed changes I made.

Fire spell projectiles: 2500-3200 --> 1000
Frost spell projectiles: 2500 --> 1000 (Frost Storm from 512 to 500)
Shock spell projectiles: 1000 (lightning bolt/chain lightning/thunder bolt changed from instant beam attack to missile attack so you can actually dodge those)

Spider split: 2000 --> 1000
Chaurus split: 2000 --> 1000
Dwarven spider shock bolt: 1000 (changed from instant beam attack to missile attack)
Dwarven sphere bolt: 3600 --> 2500
Riekling spear: 2000 --> 1500
Ash Spawn projectiles: 2200 --> 1000
Ash Guardian projectiles: 2500 --> 1000
Seeker projectiles: 1200 --> 1000, 600 --> 500

Dragon shouts/projectiles: 1200-2500 --> 1000

All arrows: 3600 --> 2000, gravity 0.35 --> 0.2
All bolts: 5400 --> 2500, gravity 0.35 --> 0.2

Note: Cone/Rune/Master spells are not touched. Non-damage spells which are not used by enemy are not touched.


Compatibility
Any mods that changed the Projectile records are not compatible but can be easily patched. I suggest to check in Xedit to see if there are any conflicts.
If you want to apply the changes to your custom spell or arrow mods, just follow the above reference and tweak them in Xedit. (All spell speed are standardized to 1000. )

Action Based Projectiles Patches for Random Mods by deskydesky.
Action Based Projectiles Patches - RoM and Mysticism by Blackread.


Recommendation
True Directional Movement - Modernized Third Person Gameplay
Enemy Magelock - NPC Magic Casting Commitment


FAQ
Q: Most archery mod increase the speed of the arrow, why do you reduce them instead? 
A: Most archery mod is built for player shooting experience in mind and increasing the speed makes it easier to hit. But it makes enemy archers super deadly and unfair. Also with True Directional Movement's lock-on and predictive projectile aim support, you don't need insanely fast arrow speed to hit anymore.

Q: I can't hit enemy with spells! They are too slow what do I do?
A: Use True Directional Movement's lock-on and predictive projectile aim support. If you still find it hard, use homing aim support and you will never miss if there is no obstacle between.

Q: The projectile speeds are still too fast! Can you tune them further down?
A: You can tweak it pretty easily in Xedit. I only provide the version I use.


Credits
(SGC) Dodgeable Arrows Spells and Shouts by distar66 for the inspiration and reference.
Odin and Apocalypse by Enai Siaion for the new shock spell assets.