Take a look at the private keys from your Bitcoin Core client. They should look like mine (the following are keys from the testnet):
Now go to your Electrum and take a look at your keys there (...
I don't know how to do exactly what you are asking, but I think you could use some wallet like Wasabi. Run it on the offline laptop with encrypted disk, and connect to local full node (bitcoind running on your online laptop) through local IP address. You can configure Wasabi to do that in the settings.
I use similar setup where my Wasabi wallet connects to a ...
A couple of times I noticed a slight discrepancy between the fee that I did broadcast (always 1 sat/byte) and the fee (1.2-1.3 sat/byte) that was shown in the blockchain explorer. Such minor discrepancies suggest to me that Electrum somehow automates the process of bumping the fee up when needed.
Most of the times its above 1 sat/byte (it should be sat/...
the Electrum wallet downloaded from the Play Store is heavier than the app downloaded from the Electrum website.
Reason for difference in size: https://stackoverflow.com/a/66419404/
So, you may see different size in Google Play Store based on Android device.
This raises the question of whether the Google Play Store is fundamentally trustworthy?
@Prayank confirmed that yes, it's your fee rate and provided some sites you can use to check the state of the mempool - and hence the fees that fit with your objectives - before sending the transaction.
Additionally, if you want to INCREASE the fee of your transaction AFTER you've sent it, there are a couple of ways to do it. The simplest way is called ...
BitPay is literally the worst choice you can make for Bitcoin payment processing.
BitPay routinely requires your paying users to provide sensitive document scans even for the smallest amounts like $10 - killing payment conversion, is very outdated technology wise (always has been), and was Bitcoin explicit enemy in the past (now kind of neutral).
If you ...