Not to take away the one redeeming feature of the Touch Bar for you, but have you looked at hot corners for locking the screen? I find that even less friction.
This is how I lock my computer at work. Just slide all the way to the left bottom corner. Done. Really like that feature
Control+Shift+Power turns off the display and by checking "Require password after sleep or screen saver begins" in System Preferences you get same effect by using a keyboard shortcut. https://apple.stackexchange.com/a/46170
Personally I prefer hot corners because I can lock it with one hand, sometimes as I'm in the middle of getting up.
I do a shift modifier on mine and then just throw my pointer into the corner. Works well enough for me!
Ctrl-cmd-q locks out of the box, no customization needed.
For me, Hot Corners are a pain when they're accidentally activated, so another way is Apple menu -> Lock Screen. After about 5 seconds, the screen turns off.