Well, it's been years (like 15 or so) since I gave it a go, really, so maybe I should try again. But, yes, holding Ctrl and then pressing X and then S seemed too cumbersome for an ordinary operation like saving your buffer (or frame?).
Back then I was also using vim in mswin mode where Ctrl-S would save the file, just like in Windows.
Interestingly, though, I still find :w<Enter> easier. Maybe it's muscle memory now, maybe because I don't need to hold a second key for two key strokes, maybe colon is easier for me, maybe...
Just a nitpick, emacs is every bit as "modal" as vim. If you configured vim to start up in insertion mode and had to ^O to do every normal mode command, it would be somewhat close to Emacs's fundamental-mode.
C-x enters a keymap called the `ctl-x-map`, lots of file-related commands live in there but also half a million other things. It's very similar to `:` to enter an ex command or, more accurately, `g` as a prefix to a million different vim commands.
If you ever find yourself in emacs again, try typing C-x (to enter the `ctl-x-map`) and then hit C-h. This shows the help for the Ctrl-x keymap, and you'll see it's somewhat well-organized, if completely arbitrary. For instance, if you hit `C-x 5` you'll be in a sub-keymap (the ctl-x-5-map) which has a lot of frame-specific management mappings. Why is it under `5`? Historical reasons, no doubt, but it's inscrutable to normies like me.
shift semicolon w enter
ctrl x s
(Flaming in jest and good heartedness)