Electron is like almost any other cross-platform VM, including Java (which is living under most of the "native" apps on the world's most popular platform), .NET, and so forth. It doesn't share resources between instances but then you also don't get dependency hell (wrong version of Java for application X, etc.)
Subjectively, I'd say that Electron's performance overheads are not bad compared to, say, Smalltalk in the 90s, where one Smalltalk application could bring a fully loaded state of the art workstation to its knees.
And don't get me started about Flash. I had a whole project cancelled after an engineeer brought up the CPU meter during a fairly simple animation.
I've never seen anything performant built on top of Smalltalk, including the Xerox Star's built in apps which were developed by universally acknowledged geniuses. Flash's performance issues were legion.
Chrome is widely considered the best current desktop browser in a very competitive space. If it has problems it's definitely in idle power consumption (which indicates wasted idle CPU) but it is used by a hell of a lot of people who have free alternatives.
Subjectively, I'd say that Electron's performance overheads are not bad compared to, say, Smalltalk in the 90s, where one Smalltalk application could bring a fully loaded state of the art workstation to its knees.
And don't get me started about Flash. I had a whole project cancelled after an engineeer brought up the CPU meter during a fairly simple animation.