Thanks for posting and sorry to hear you are experiencing lag.
There doesn’t seem to be any lag on this end (beta enabled as well), but it may be specific to a project. Is this happening with all of your projects? Can you share a Read-Only link of an affected site? Feel free to contact us directly if you aren’t able to share the link publicly.
Regarding the CMD/CTRL + Backspace shortcut – I’ve notified the team of this and we will investigate to get this resolved.
I’ve been experiencing laggin designer as well. In Safari and Chrome. I found other posts and followed steps to disable plugins etc. but that doesn’t help. I prefer Chrome (on version 66.0.3359.181) but it’s still burning up my CPU. Fan always blasting when in Webflow only. As soon as I quit webflow, fan stops and computer back to normal.