In standard usage, I am using splits (horizontal). The only real time I am using buffers is when I open up multiple files from command line in some type of ‘vim ‘git grep -l “<search>” .’‘ scenario where I will do an action against all opened buffers in vim.

Regarding your second point, I behave similarly. If I am off in one of my non main editor tmux panes and I need to open a quick file, I will do it there instead of moving back to my main editor vim session. This is usually due to the file needing to be opened is outside the cwd of the main vim session.