tin...ATMs are widely available...Yangon Mandalay (and both their airports), Bagan Nyaugnshwe, Lashio, Hsipaw, Mawlamyine, etc etc. basically everywhere a typical tourist will go, unless you go quite off the beaten path small towns. You just need to check with YOUR bank that their cards will work there (ie. some banks block / blocked their cards from use in Myanmar).
Kyat can be used to pay for everything now, so you only need to take a currency to buy your Kyat with...($US Euro and Singapore $ accepted nearly all official money changers)...$US can be used to pay for accommodation, but not the other currencies.
IF your currency is $US then take some, but any notes must be in pristine condition (no marks, tears, creases, fading, etc). Not sure about the 'blue line' but think it is just nothing pre-2006.
ATMs - have a 5,000 Kyat local bank fee and withdraw up too 300,000 Kyat per go, more than once a day if required. (some reports one banks ATMS are 6000 fee and only 200,000 Kyat)