If I can make a recommendation, I draw in Clip Studio Paint, save my images at full size, and then size them down in Photoshop with the Image Resolution setting. 750 is the maximum width so I just use that and it's usually enough. I don't have as many issues with grainy images or anything so if you have Photoshop, try doing it that way, might get you better results. Then you can just save it as JPEG in the program without having to go through any weird conversion methods (and if that's how you're doing it already, maybe consider drawing your original files at bigger sizes, if you're forcing yourself to work small for image compression sake? It's much easier to start off bigger and go smaller than to try and make a smaller image bigger).
Also, I know it's unrelated, but the site being blocked on your school's computers isn't really their fault and so I don't think it really counts as a "con" What websites are blocked on your computers is typically based on the school's servers and what they pre-determine to be a blockable site.
Either way, so far I'm finding not only my traffic, but my reception better on Webtoons as well, in terms of user interaction and comments and such (which is ironic because comments on the episodes are the only way for creators and users to interact . . . there are no wall posts, no forums, no private messages, no profiles, even. Maybe that's the reason why people interact more on the comics themselves.