Mixing armor will also level up the other types, this is nice even before you get the undaunted passives who take time to level for new players.1. Yes, @DigiAngel. The dolmen train leaders in Auridon and Alik'r have the Autoinvite add-on set to "x" and "y" to collect players from zone chat into the group.
2. Having at least one (1) piece of each armor weight maximizes your base attribute stats from the Undaunted Mettle passive (in the Undaunted skill line). See the very bottom of this link to the UESP under passive abilities: https://en.uesp.net/wiki/Online:Undaunted
3. Yes, I use the UESP build editor quite frequently. https://en.uesp.net/wiki/UESPWiki:EsoBuildEditor On rare occasions, the stats are a few points off (especially right after a major update) ... but it's easy to use, draws info directly from the game, and allows saving. You can also use the PTS server to create character templates without committing resources on the Live server.
1. Zone Chat is pretty much a cesspool. Don't use it unless someone holds a gun to your head.
2. Undaunted Mettle -- a vastly overrated passive that: "Increases your Max Health, Stamina and Magicka by 2% per type of Armor (Heavy, Medium, Light) that you have equipped."
The buff received is utterly MINOR especially when weighed against the BONUS received from wearing SEVEN pieces of the proper armor for your Class. ANY decent tri-stat food buff (Bewitched Sugar Skulls) will give your MUCH MORE stats buff and you can have your seven-piece armor passives which are excellent. Wear SEVEN pieces of the correct armor for your Class to receive maximum buffs and forget that "mixed armor" nonsense.
3. Build Calculators are for teachers. "Those who can, do; those who cannot, teach." And use build calculators.