Hey, sorry for the delay in getting back to you!
If you are looking for max efficiency, try and aim for a Level 10 Vault whenever you can. Levels 11+ still provide some solid rewards, but the reward efficiency is highest up til Level 10. Picking what Regions to get rewards from is a matter of what excites you, but if you are not sure what deck you want, consider taking each region to 4, then each to 8, 12, 16 etc because every 4th level in a Region is a bit more efficient in terms of the reward you get.
Regarding duplicates, the Shard values for extra copies are 15 (Common), 60 (Rare), 250 (Epic), and 750 (Champion).
Epics and Champions have duplicate protection whenever you get a random card from any source, which means you will always get an Epic or Champion that you don’t have 3x copies of before you get Shards instead. The way duplicate protection works is that we check any Set restrictions followed by Region restrictions.
For example, Levels 21-24 on Freljord are currently set up to award Rising Tides cards first. So, if you are given a random Champion, the game first checks to see if you have 3x Sejuani first (the only Freljord Champion in Rising Tides). If you do already have 3x, the game then will give you a random Freljord Champion from any Set. If you have all the Freljord Champions, then you would get a random Champion from any Region/Set, and only if you have all Champions period will you get 750 Shards. Epics work the exact same way.
Rares and Commons don’t have built-in duplicate protection though, so if you have 3x Mystic Shot and would open a 4th, instead you get Shards. This helps players get some Shard early on beyond what they would open in Chests and provides a bit more agency for players to craft what they want to craft.
Currently there is no way to directly earn Coins by playing, and yeah, we did shuffle things up a bit by making Shards the earned currency and Coins the paid one haha.