It doesn't show the exact size... but you can roughly calculate it using the standard formula:
the size of the tx will be: 180 bytes per input + 34 bytes per output + 10 bytes.
That was what I was asking and I appreciate your will you tried to help me first!
I understand the calculation you wrote is a rough calculation that provides an estimated result for the tx, but it may be different in real because Mycelium tries to optimize the transaction. Well, even an estimated result is better than having no idea so I thank you!
Mycelium starts with the oldest output and adds more until enough value for the transaction was added, then goes through the outputs and checks whether some can get removed again.
...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.
I can further add to the discussion that I use both core and Mycelium, but for very different purpose.
I use core when I receive payment for trading etc. in other words relative large amounts that I need to keep safe. With core am I in full control. I run it on a dedicated PC. Downsides, its slow to sync, slow to start... but it is OK, since only actually use the application once in a while to "unload" my balance to other addresses.
For everyday use do I use Mycelium, I have found it to be extremely reliable, and the "priority" system works well, if setting to highest priority then does the tx always gets calculated in such a way that I my tx gets a priority for confirming (nothing is more frustrating that having a tx stuck in a medium priority when buying something). I also have the "normal" priority if speed is not an issue. I also find the "cold storage" option really useful, my favorite storage mediums are paper wallets, Mycelium is
excellent in quickly sweeping these with the phone camera. I can sincerely recommend for day-to-day use. There is some apparent security issues, but they can be mitigated by not having large sums on you Mycelium wallet, since it is so easy to sweep paper wallets, it is very easy just to sweep a paper wallet to "fill up" your Mycelium wallet when needed.