The patches will be easy to find. It's the kit that will be slightly more difficult depending if you want the PI version and if you want it in SS like Gigi wears. Take a look at this link: https://www.classicfootballshirts.co.uk/2016-columbus-crew-player-issue-gk-shirt-clark-1-very-good-m.html...
Even with a heat press, they can't remove it. You can try an adhesive remover.
General consensus is to go one size up authentic in comparison to replica.
In my opinion, these are way more snug than both of those. In comparison to comfortability, I would say the React is much more comfortable. I had to size up on both Flyknit Lunar & Lunar Epic and went TTS on these. I've used all for running and after just a few runs I can say these are great!
You can also Google the style code on the tag to check if it's legit.
Also, some Player Issue kits are starting to have a 'Made In' stamp as well as a tag inside the jersey with the style code and size.
In my opinion, these are true to size. Initially I thought .5 size up would be better, but I find TTS works just fine. Coming from someone who went .5 size up in the previous Epic versions.