There are also plenty of markdown preview packages available for both Vim and Emacs (even live preview). Emacs has had preview-latex since before Atom even existed.
What is a mode? It is when key presses do different things depending on the mode (e.g., normal vs insert mode in vi). Emacs very much has modes, by default, and many more of them than Vim (or vi), including multiple vi-like modes. Emacs is so much more modal that it is trivial to implement vi/Vim modes in Emacs (and notably the reverse is not true).
Just because Emacs does not enable the exact three or four mode key binding sets that vi/Vim does on an out-of-the-box startup does not make Emacs "not modal". vi/Vim does not own the concept of "modes" by implementing three or four very specific mode key binding sets; lots of software implement modes and to put it somewhat confrontationally, Vim users tend to be a bit full of themselves thinking that their modes are super special (and I say that as a former Vim user; I still occasionally use vi, but not as a primary editor).