I'm glad you brought this up. At Gardening SE, we un-embiggen many photos, because we ask for a lot of them and they can take up a tremendous amount of space. If the OP posts them very big, often we who edit will come along and make them smaller, and I've wondered whether or not I should do that here.
For the best of both worlds, you can make your picture smaller in the post, but link it so when people click on it, a separate tab opens showing the image in its original size. It's a little bit time-consuming, but very easy once you get the hang of it. I find it much easier than cropping the photo first. I almost always re-size images to medium. They're still easy to see in the post, and can be seen larger if desired. Using the method described below, I resized 6 large photos down to medium in this question. It looks clean and people can check out the larger sizes if they want.
With respect to @James Jenkins, I'm going to illustrate it using his answer you referenced.
Using the insert photo icon in the question/answer box, the SE system will upload the image with a link to itself in its own tab. The number in the last bracket is that link. In this case, 1.
[![weed burner image full size]]
To make the picture smaller without connecting to the larger, add one of the size letters to the end of the url, just before the .jpg. That's what he did with the “t”. (See chart below for size choices.)
Clicking on that picture opens a page with that picture in the small size.
If you want to be able to see the large picture by clicking on the small picture, it takes two steps.
First, copy and paste the original image address, but give it a unique identifier by adding something onto the number in the first bracket. I use a small “f”, which to me stands for “full-size”. Some people use numbers or other things.
Second, to link the two so that clicking the smaller will show you the bigger, add the f to the bracket box in the original string. In this case, 1f.
[![small weed burner image linked to original full-sized image]][1f]
Now when you click on the small image, it shows the original size large one in a separate tab.
To make sure people know you did this, post a little message like: Click on pictures to see larger view.
SE uses the sizing according to the Imgur system. This is a chart of names and sizes to help us choose what we want to use when posting or re-sizing.
(I've posted medium (m) and large (l) just for reference)
This is medium, 320 by 320:
This is large, 640 by 640: