Sorry for the late reply, forgot to check this lol.
Dragging and dropping images will lead to significantly lower quality than even just clicking the "save image as" option though I don't reccomend this. What I would advise you to do is either look up some type of "Pixiv image downloader". There are lots of like chrome extentions, tampermonkey scripts, etc that you can find that allow you to download the image as a higher quality. Though it's inefficent, personally I use an extension called "Max Image URL" which tries to find the highest quality image that it can, then I would just download the images given. If you have any questions about it, feel free to ask me.