If you're using Cinnamon, are you using hardware or software rendering? The software rendering mode is a lot slower and could be responsible for your choppiness/image load time issues.
It's also worth mentioning that Mint is kind of a franken-buntu, and neither Mint nor Cinnamon (by extension) have very many contributors or much financial backing.
The big 3 distros that have major corporate backing and share a codebase with enterprise solutions are Debian (Google, Ubuntu, et. al.), Fedora (RedHat) and OpenSUSE (SUSE). KDE and Gnome are the two most mature desktop environments, which consequently have the most contributors (although KDE has more in common with its original codebase than does Gnome, and requires far less memory).
With more money and contributors any of these 3 communities will achieve their development goals more expediently than a small project like Mint. This generally translates into a more reliable platform. Here's some good reading on these subjects:
https://www.makeuseof.com/tag/companies ... x-distros/
https://www.zdnet.com/article/google-mo ... x-desktop/
You can attach images using a URL, the forum just doesn't support image hosting AFAIK (kind of like Reddit). I usually upload images to my website and link to them, but you could use dropbox, onedrive, google drive, imgur, imgbb, etc.
The tag is [Image]url[/image] or you can use the little picture-looking icon in the bar on top of the editor.
Hope that helps.