Quote from: eiger3970 on September 17, 2024, 11:17:18 PM

Seems like 1 offline computer and 1 online phone would work just as 1 offline computer and 1 online computer.
1 offline computer and 1 online phone is better suited whilst travelling.
Therefore, I'm wondering with the send transaction, how as currently my offline computer TailsOS USB Electrum says no funds, but I have successfully received funds to the offline wallet.

Simple explanation is: Electrum doesn't store bitcoins.
Instead, your offline Electrum contains your "private keys" and your online Electrum contains your "public keys".

Electrum simply shows transactions associated with your public keys which are requested from the connected server.
With it, Electrum can create unsigned transactions that spends those outputs.
Anyone can do that if they have your addresses, public keys or xpub but no one can sign to finalize those transactions without the correct private keys which is in your offline computer.

Quote from: eiger3970 on September 17, 2024, 11:17:18 PM

I'm trying to adapt this video process, but I guess the online phone which doesn't take USB sticks, would either use a QR scanner or I would have to manually type some details into the phone's online hot wallet (it's an iPhone, so no Electrum app).

The iPhone wallet app where you will create a watch-only wallet should support Electrum's PSBT transaction format and the QR code's base43 contents.
Otherwise, it wont be compatible. Telling the name of the app should be a good pointer to tell if it's compatible with Electrum.