Here are the dimension I’m using for posts, just for comparison with others.
So for all exports, WP/LR plugin included, I export pics at 1600px on the longside with sRGB colourspace with a limit of 395Kb for the file size. I tried less and ran into trouble. I set dpi low, but I don’t think it’s relevant for the website.
What do you think? What settings should be fine for your uploads?