Not sure if these things are known; but after running into confusion about archery damage (specifically thinking that my arrow damage was multiplied by five randomly,) I decided to run some tests. Since I'm new, I do invite people to double-check these findings, especially PC users who have the console.
No mods installed; version 1.5 on PC.
1. The damage tooltip is wrong:
-Set Marksman skill to 0 (eg, player.modav marksman -X, where X is your current skill)
-Equip an Orcish bow (10 damage) and then unequip the arrows. You should see 10 damage on the bow, and on the tooltip.
-Equip Iron arrows. You should now see 18 damage on the bow, and 26 on the tooltip.
-Equip Nordic or Steel arrows. You should see 20 on the bow, and 30 on the tooltip.
What is happening is that the arrow's damage is counting twice - once on the bow's damage, and once on the tooltip. The tooltip addition seems to be false.
When I tested outgoing damage, I got 18 damage with iron arrows and slightly less than 20 damage on Nordic. Tests were done on a Draugr Wight fff000de6 with forceav health 2000 and unconscious.
2. Arrows are affected by (nearly) ALL bow damage increases:
-Set Marksman to 100 (from the previous test, player.modav marksman 100)
-The bow's damage with no arrows is now 15. With Nordic arrows, the bow damage goes up to 30(!) and the tooltip to 40.
-The draugr took 30 damage.
-Conclusion: Archery skill affects arrows the same as bows: base x (1 + skill/200.)
-Add 5/5 Overdraw. Bow goes up to 60, tooltip to 70. Draugr takes 60 damage.
Conclusion: Overdraw affects arrows.
-With only 3 +40% enchants (three items of Peerless archery,) the bow went up to 132, tooltip to 142. 132 damage.
Conclusion: Fortify Archery enchants affect arrows.
-Of course, smithing boosts on the bow won't affect arrow damage. Didn't test alchemy, admittedly.
3. Archery backstabs DO count enchants!
-With 100 skill, 5/5 OD, and Deadly Aim, the archery sneak attacks returned 180 damage (60 x 3.) This is still the Orc bow with Nordic arrows.
-Adding the three +40% enchant items, I brought my draugr down to 1604 from its full 2000: 396 damage! As this is 132 x 3...
Conclusion: Enchants are counting for sneak attacks with archery.
In another test, by the way, I ran a Mystic Bound Bow with 100, 5/5, DA, and 3x40: 341 tooltip (317 bow damage rating.) 290 standing damage for some reason, but a 951 sneak attack.

