I've found that the creation kit render window is quite a bit different from the game. contrast, gamma, etc etc is different enough that lighting is a pain in the ass.

Is there some window somewhere that I can make the render window output closer to the game?

check preferences, there's a lot of settings for what and what not to render.

might also be some additional ones in editor.ini

also, check your render window light settings. the light bulb icon means auxiliary light (a to toggle), and next to it, there's buttons for effects, sky, grass etc

I'm talking about the general output of the window, not individual light settings. When doing lights, the render window needs to be "over bright" relative to the game.

Can that be changed?

I've also found that my rendor window in the ck looks much darker than when I am in game. It would be nice if there was a fix.

yeah if there were video output settings in an INI or something, that'd be fine. . . of course, that would probably mean you'd have to restart it after every change which would make the whole process take a year or 2.

Turning on Sky and FX gets the render window very close to the game, at least for me.

Beyond that there's not much you can do. The CK is not running a lot of the graphical processes that the game runs, thus causing it to look slightly different. Having them on could cause severe performance issues and dramatically impede your ability to work on spaces so they are not included.