If I choose to go towards the light armor path of the smithing perk tree, once I get 100 and choose dragon armor, can I choose daedric as well? i.e using perks can I go Steel>Elven>Advanced>Glass>Dragon>Daedric or do I have to spend points on the orcish/ebony/dwarven smithing perks first to get Daedric???

You need to work your way from the bottom up.

No, if you want to smith daedric after the light path you have to go up the opposite side of the tree. I'm happy with over-smithed and over-enchanted glass weaponry with light armor though.

hmmm, but you can get dragon armor if you go up the daedric armor side correct? I'm mostly curious because I like using Light armor (which Dragon armor is) but I like using weapons from the heavy armor categories...

Yes once you get to 100 skill if you want daedric you have to start on the heavy armor side, for this is what happened to me -_-

You can reach Dragon Armor by going up either side, but you cannot go past Dragon Armor and "descend" down the other arm from where you started.

The anvil shape of the constellation seems to be causing a lot of confusion thanks to the "peak" being far less pronounced than most other perk trees. You don't see anyone complaining about not being able to get "Block Runner" after getting to "Shield Charge" by going through the Bash side and skipping "Deflect Arrows".