usability – Let users choose a value’s unit next to the value input field

In our application users/developers are able to build their own web layouts via editor. Therefor, they need to define container sizes with either percentage (%) or pixels (px).
Currently, this choice can be made within the input field. I did not even know this until a co-worker told my about it – the placement of the unit choice within the input field was just not obvious to me and is difficult to learn for new users.

Current solution:

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I came up with two alternative solutions:

(1) Choose the value’s unit via toggle switcher

(2) Choose the value’s unit via dropdown

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One drawback I’m aware of is that the form starts to look more cluttered.

What are your experiences with use cases like this?
What are your thoughts about these alternatives?