Hi, I would like to understand a little more about the bitcoin core wallet and if it is cross compatible.

Is it possible to create a watch only wallet in electrum . Feed in the public address of a bitcoin core cold wallet.
Create a psbt with the electrum watch only wallet and save to file.   Then where it says load psbt file in bitcoin core v21 just load in that electrum generated file?

Is that dangerous or perfectly fine and long as the change address is the same as the sending address?
Are psbt created with electrum cross compatible? Some people say yes some say no. I don't know who is correct and I can find no mention of importing an electrum watch only wallet generated psbt file into a bitcoin core wallet.

If that is possible and you can sign on the airgapped bitcoin core wallet you can then somehow export the signed tx in hex format and send on the internet enabled full bitcoin node?

I just want some others opinions on feasibility of this process.

Also, this may seem a strange question. But when you create a bitcoin wallet years ago then you also encrypted it with a long password.
If someone only has that password but no access to the wallet.dat file then your coins are safe even if they have the public address?
How can keyloggers steal peoples bitcoins if they can see the password you will type but they can not grab the wallet.dat file?
Or do keyloggers also easily take that wallet.dat file off your machine easily?

Thanks.