Rumbletiger, Keklin, and delericho are right.
And I'd XP you again Dandu but apparently I haven't spread it around enough, what with me not reading/posting much in the past year.
1: Magic armor and clothing generally adjusts itself to fit the wearer, as described in the DMG.
2: There are no encumbrance mechanics of the sort you imply; vests or robes or shirts that are not specifically noted as armor do not impose any armor check penalty, though the items may have a weight listed, and you always count the weight towards your total carrying capacity.
3: There's no requirement of any kind about needing skin contact or nearly-skin-contact to benefit from a magic item, you just have to be wearing it in the appropriate area (no wrapping a magic necklace around your forearm and trying to make it function as a magic bracelet). There's just a game-mechanical restriction against benefitting from more than 1 magic item in each "slot", which is pretty abstract in the first place (many magic items are likely to physically overlap to some degree when worn, like a magic ring worn under a magic glove). Nothing physically prevents you from wearing 10 or even 20 magic rings (fingers and toes), only game mechanics. Which say nothing about needing skin contact with a magic item.
Just cuz I'm a nitpicker.