When I created a 'Project' posting which needed many photo's, I was advisded by MikeK to always use [Full Image]. However, I always create my images in .PNG format - never ever in .JPG - and control their size to about 8 - 10 cm wide at 200 dpi which gives a final file-size less than 1.5Mb.
I'm sure you are refering to
@Stigmorgan posts which always contain many images and I've just evaluated the last one he posted - - - - it is 34.9Mb!!! only 96 dpi but 80 x 106.68 cm -- converting that to 200dpi and 8 x 10.67 cm brings the size down to 1.51Mb and the compressed file as held on disc (and transmitted via 'tinternet) is 628Kb - about 1/55th of the size which directly equates to bandwidth needed.
So, - - - I suggest that rather than use [Thumbnail] images it would be preferable to always edit the original image to control it's size.
For a direct comparison, here is my version of the image . . .
View attachment 161397Though I've also made it smaller in the forum software and in fact I would normally also crop most of the background which will further reduce the bandwidth needed.
View attachment 161398
The second image is only 302Kb on disc and 728Kb expanded.
What I'm saying is that it is incumbent upon anyone posting images to minimize the size prior to 'attaching'. There is no degradation in the quality of the information provided so (to me) there is no argument.