Is there a way to render without creating a file?

[Rangler]

Just to check the clipping and headroom of the entire project?

[Robert Randolph]

Use a good meter on your master like https://youlean.co/youlean-loudness-meter/ or http://www.tb-software.com/TBProAudio/dpmeter2.html

Then you can simply clear them and hit play.

You're more likely to just keep checking them throughout the mixing process though.