Dynamic Form Fields, add remove button UX

Is it good design if in the below form, in which I require user input, the plus button gets disabled if there is no input yet?

I prefer this rather than hiding it but are there any better alternatives to introducing a disabled state? On a second note, what would be an appropriate color in the below for a disabled state for the green button?

Is it good design to have the input being saved without some sort of confirming as user like pressing the green button? I found testers wondering if the input is used without confirming anything (like pressing the green button). How to make this experience better?