Lets say you have some dark dungeons mod which makes it really dark except in places with torches. Wouldnt you be in quite a spot frequently? Since you can't hold a torch and wield a bow at the same time

I've played a lot of two-handed sword users and they have the same problem. This is actually one of the reasons why I never use mods that darken dungeons. I just don't find it very fun to lean forward and squint into my monitor.

My characters keep their torches constantly equipped while in most dungeons. Sheath the weapon and - hey presto! - the torch is back in the character's hand. It disappears when the character unsheathes her weapon again. If only things in so-called real life were this easy.

Of course this doesn't help during the actual fight. If you're absolutely hell-bent on using a darker dungeon mod it is probably worthwhile to get a mod that will let you drop lit torches. This provides pretty good illumination most of the time.

As Pseron said, bow + torch is nice in a way because equipping your bow extinguishes your torch when foes are near.

My character primarily navigates dungeons by where the pink glows are (she has gear that gives her loads of detect life). She thereby knows where the foes are and knows when it is safe to pop out some light if need be. For this, she has tried night eye, light, torches and they all have pros and cons. Currently, she simply casts an extremely weak frost-on-target spell that lasts about 15 seconds. It ‘sticks’ when it hits something and lingers providing a nice light source and she can cast several if needed. This is very handy for checking dark corners for treasure chests and such when her detect life tells her there are no foes nearby. Her biggest hazard doing business the way she does in a dungeon is traps. She has learned the telltale signs and moves slowly and cautiously, but still sometimes get caught by them.

If you are concerned about navigating in very dark dungeons and really want to see, equipping a night eye item is probably the way to go. It lets you see everything but does not give your position away to foes. The ‘problem’ of not being able to see where the shadows are to stay in them is way overstated. A sneakster worth their salt can learn where the shadows would be and a high stealth skill really makes it a very very minor point. The reasons I prefer not to use night eye are two: It detracts from the atmosphere in the dungeon for me, and it makes those critical pink glows a little harder to see. (Yes, I’m aware that there are mods to change night eye for those who so desire.)

So for my character, detect life gear is the answer. We find it actually ‘maps’ out a dungeon pretty well simply by the location of foes. More importantly, it avoids surprises for a very fragile no-melee skittish archer. 120 feet is probably more than enough for dungeons. My character uses 360 feet (a pair of transcendent sigil rings) primarily to avoid surprises while riding – making horse travel very safe for wary elves and fast horses.

I'm gonna have a go at the acting some other Khajiit players pull...

Mr Mistoffelees does not need lean forward and squint, can just use Cat's Eye and see in dark. Mr Mistoffelees feel sorry for races of men and mer.

It's been ages since any of my characters used bow but I remember I usually switched to one handed weapons in dungeons because I use a mod that makes dungeons darker. But there is another good mod, I think it's called sth like Dungeon actors use torches which makes NPCs equip torches in caves, making it more realistic. That way you can also see them from afar, it doesn't make sense that they would spend time in dungeons without at least one torch. Besides when you kill them, they also drop a torch which you can use. Of course that goes only for NPCs, not for skeletons, imps and other goodies.

EDIT: Here's the link to the mod: http://oblivion.nexusmods.com/mods/11169