- Weapons have roughly the same DPS, the difference is speed/damage per swing. Because there are per-hit effects which become important later, you want to go with the fastest: Swords. Also, if you are using a broken tactic like run to enemy, hit, run back before he can hit you, a fast weapon helps. By the way, daggers are even faster, but not all one handed weapon perks apply to them. (But daggers do use one-handed weapons)
- Sneak is broken. Yes, you can sneak around stationary enemies. However, once you take that first shot, hiding is ridiculously difficult, so sneak contributes little. Also, a lot of enemies pop-up behind you or attack you due to a script or whatever, so you get no chance to sneak. Bosses, being the strongest enemies and the target where sneak attacks would be most useful, can't usually be sneak attacked because of the level design (an arena where the boss makes an entrance by charging you). The only exception is if your sneak is 100: Then you get the hide in plain sight perk- it's a bit buggy and you can abuse it by sneaking right in front of an enemy, which will force him to be unaware of you for a second (which is what the perk does) and then you can sneak attack him before he "sees" you again.
- Alchemy is fun, but ultimately not worth the training or the higher level mobs you will get due to extra levels- all you need to make is health and maybe mana potions, both are very easy. Enchanting is fun but you can get magic items easily anyway. Smithing is, again, fun and lucrative, and I'm not sure if you can get dragon armor (best in the game) without it, but for other things it's not hard to find powerful items anyway.
- Speech is useless. Persuade/intimidate attempts are rare, do not have interesting dialogue paths, and the rewards you get are shit. Speech itself affects your merchant prices, but even with 100 speech you still get ripped off (they sell at double price and buy at half) and with crap speech it's not that bad (sell at triple buy at third) so yeah. Money is very easy to get in this game, anyhow.
- Pickpocket is pointless, you can simply quicksave and quickload until you get the item. There is also a bug where having too high a pickpocket score can make you success go from say 13% to 0%.
- Lockpicking is useless. Lockpicks are common, cheap and light. The minigame is very easy, even for hard locks. There are very few doors you actually have to pick.
The best weapon is sword. The best spell schools are destruction and alteration (+ to armor spells like oakflesh). Illusion is nice because it has invisibility and light spells, but they are not useful in combat. Restoration is nice for healing, but those spells are too expensive and you will not have mana left for offense, or really anything besides occasional bursts of healing. Conjuration has bound weapons, which are nice, but the summons require obscene amounts of mana.
So yeah. Keep in mind that I'm far from finishing the game.