So, with Mycelium BTC Wallet and a portable device that can run Android, can I create my own "hardware wallet"? I find it awesome.
Well, kind of. Usually when people talk about "hardware wallets" they mean some kind of device which can't be hacked due to the code it runs being very limited in scope, and uneditable without physically pressing some buttons on the device. Android on the other hand is a general purpose operating system and probably has many vulnerabilities and possibly even deliberate backdoors.
...and if you wanted to send 16, it would choose the first four ones then remove nothing because 5 + 5 + 1 + 5 is 16 exactly. I hope I understand right, thank you! I could appreciate a feature to select my output option and also information about the exact fee before transaction, though.
If the 16 included the fee, yes, but probably it doesn't. In which case 5+5+1+5 isn't quite enough because you need to fund the tx fee as well.