I have done some benchmarking of Qt/C++ vs Eletron/node performance while I was working on rbkit-client (https://github.com/code-mancers/rbkit-client) and frankly performance gap is huge for stuff like parsing, processing and anything which is CPU bound.

So if Nylas is parsing imap messages then both parsing and rendering difference between a native and eletron app will be big. Fortunately browsers workaround some of this problem by consuming json and stuff - formats browsers can natively parse.