I am using Electrum since a longer time and I am satisfied with it.
However I am thinking about a situation users want/need to migrate his other BTC client from/to Electrum.

Is there a way to access the own wallet somehow with another Bitcoin tool?

In other words is the electrum wallet file (not software) GUI/software independent?

This question arises for the other direction as well:

Can I open wallets created with other BTC clients with Electrum too?

What If a user wants to migrate from one BTC GUI client to another?