Thanks!
What i had heard, was that if you only withdraw some of the amount from a paper wallet, the change might somehow ended up on another address?
Oh yeah, sorry i forgot about that (forgot that sweeping transfers everything). All of the BTC will be in your mycelium wallet, if you sweep the paper wallet. There is no change at all, it just transfers the balance from private key and transfer it to mycelium generated keys.
Don't worry about it, you are good to go! However for sum like 3BTC, you should get Ledger Nano S or Trezor as both are around 100$ at most

Nano S supports more cryptos than trezor, and they are pretty user friendly as well as the generation of the seed is really secure as the seed is never shown on the computer screen, nor it does ever go to the computer.