That last part goes a bit over my head but I am sure with time I will naturally comprehend.
Discussion
To keep it simple, Muun is a bitcoin on-chain wallet with lightning "on demand".
So it's unusable during high fees, losing the utility of Lightning network, which is supposed to be a alternative to higher on-chain fees.
It's safe to have a second "true" lightning wallet like alby, blink, wos, zeus, phoenix.