Thanks for your tips.
Finally, for bitocoins, I am using Electrum in a pendrive, containing my private keys (using a 24 words seed). On the smarphone I configured a watch only electrum just importing the master public key.
For few amount of altcoins I am continuing using Trust Wallet
Maybe I misunderstood, but seed words should always be offline - whether it's writing them down on paper, engraving them on a metal plate, or something similar. Any way of storing them where they can be exposed to online threats is not good.
As for a watch-only wallet, that's a good idea - because if you just want to have insight into your transactions and generate new addresses, you don't need anything more than that.
I think that Electrum, if used correctly, is comparable with an hw wallet, don't you think? I mean, a pen drive used only on non connected device, a watch only wallet on smartphone.
Thanks again
Electrum is open source and as such can be considered secure if used correctly. The safest way is to use it as a so-called cold wallet - which means you generated such a wallet on an offline device that has no communication with the internet - and on the other hand you have a watch-only wallet with which you can create a transaction, and then transfer it via a USB stick, QR code or SD card to an offline device where you have Electrum with which you can sign such a transaction, and then return it to the watch-only wallet and broadcast.
This procedure is described here in a very simple way ->
https://electrum.readthedocs.io/en/latest/coldstorage.html