Here's the primary issue...
People will assume that a portfolio only contains original work. And they will assume you are at least partially responsible for some of that original work if the work was a collaborative effort.
I've never met anyone who assumed portfolio work was a "recreation" of something unless the piece noted that it was a recreation on the art itself. Or was side by side with the original which was copied.
In most instances those looking at portfolios aren't really looking for how well you replicate something. They are looking for how you solve design issues. Copying the work of others doesn't show that in any way.
Even redrawing something rather than copy/pasting is still reliant on the original artist and how they solved design issue. You aren't showing any creativity or problem solving abilities even if you do "add small touches".
If you are forthright and clear about the copying then ethically you'd be fine. No one is going to fault you for replicating if you are clear that is what you have done. They will probably think you are not at all creative. However, If they find out about it later... well, you'll end up looking uncreative and unethical.
While you can show what you've replicated as long as you are clear and upfront that they are merely replications... it's not going to ever be beneficial to you. You are setting yourself up for failure from the start.
It's always best to show only original works in a portfolio for most design positions.
There are a few exceptions, such as a "web design" position looking to hire someone good at altering templates. Or a production position good at altering artwork for production needs. But typically those are specific positions looking for technical skills, not original artwork.
This is all admittedly broad generalization. But you should be aware non-original artwork in a design portfolio is really not ever favorable. Whether or not it would alter your chances of employment is highly dependent upon what the position requires and who is doing the hiring.
