I noticed a couple things when installing my TRD pro heritage grill yesterday on my 2020. Specifically about the grill upper part. I expect that this info would also be useful if you ever go back to stock or if you need to replace your stock grill upper with another grill upper with the large Toyota emblem and the chrome. While I did this on my 2020, some if not all of the info may be applicable to earlier years.
First, this isn't something that I figured out myself, but it bears repeating. For the big sheet on the top of the radiator housing, you can push in on the button in the center of the plugs to help free them. After the button's down, you can use pliers or a flat head screwdriver to gently pull the plugs up instead of prying them up. You can push the inner pins which are controlled by the button into the up position later before reinstalling them. Then after you reinstall the plugs at the end, you can push the button down to the locking position. It should be flush with the outer housing of the plug. If you push it all the way down, you pushed it too far and into the unlock position you did in the first step, so don't do that.
Second, this is something that I noticed myself. This comes after you remove the big sheet. All of the videos I've seen say that you have to forcefully pry the 6 plugs out that are under the big sheet. These plugs are a different shape than the ones that held in the sheet. They work in much the same way, but they are a bit different. Before you go pulling these up, look closely at the top of the plug. You'll see they have a similar button to the other ones. You can't push it down into a lower position like the previous plugs, but you can use a flat head screwdriver to pop the button up. You can see it's possible because the housing surrounding this button gives you room to do so. After you pop the button up, you can easily pull the whole plug up. I noticed this after forcefully pulling out the first plug. I looked at the construction of the plug and realized that I could just pull up on the button. I did my method on the following 5 plugs, and they all came out perfectly smoothly. If I remember correctly, even the official instructions say to forcefully pry it out, but it's unnecessary and possibly damaging. Of course, when reinstalling, make sure the buttons are up, place the plug in the hole, and then push the button down. It will lock in place.
Finally, this is the big one that I saw people on videos on the internet getting wrong. They say to yank the grill upper out. Some of them were kind of forceful about it. I was able to get the one clip out on the far left and had trouble with the rest. I looked at the one clip that I got out and realized how the grill upper clips into the body. I couldn't see how it all went together until I got the one out, but there are 6 clips. Have a look at the photo, and you'll see where the clips are. What I did with the 3 remaining easy clips was I shoved a long and smooth flat head screwdriver into the space between the grill upper and the body. This helped to free the clips on the grill upper from the holes on the body. After I got the easy ones free, I had to deal with the 2 more difficult clips. I couldn't come up with a better course of action than elbow grease, but at least I had more room to work with since the 4 easy clips were free. I was able to get the 2 difficult clips free without too much trouble. You may wish to lay down some masking tape before you shove the screwdriver into the 4 easy clip spots, but it would be worse to break the body than to scratch the paint if you don't do anything at all with the clips. And since you understand how the parts clip together, you can be more sure about putting it back together. You won't even have to worry about using the 2 more difficult clip holes if you're going to the TRD pro grill.