So what s the best way of keeping a wallet? portable version?
Any Electrum, whether Stand-alone, installer or Portable are built the same way as the others,
the difference is Portable has its own data directory which is the same directory where the executable is (
already explained by HCP).
As the name suggest,
Portable is for "
portable-use-case" like keeping the executable, the data directory and wallets in a Flash drive to be able to use on multiple computers (
which is risky).
The installer and stand-alone both save the data directory in your %appdata% folder,
Installer will install "
loose files" to your program files (
or your preference), while
Stand-alone will work as it is but will launch a little bit slower.
Now that you know where it will save the wallet files(s), it up to your preference or use-case now.
When it comes with security, it all goes down to how you handle the seed phrase and how strong your wallet's password is.
For the seed, just follow the suggestion above; for the password, just use the textbook instructions on creating a strong password.