Fantastic app, instabuy. I'm really happy to see these kinds of native Mac apps being successful for so long. They're a breath of fresh air amidst all the Electron crap lately.
More like to wrap a website. I doubt that it's easier than Qt when building from scratch.
I've never used both of these languages and wrote only simple things in JS but I would spend a week learning Python syntax and Qt features to deliver a better UX and performance for a cross-platform app.
I've written a logviewer with electron. Getting the custom painted table-component and column-reordering to look and feel like Finder or iTunes tables was at least 10 hours of work.
Working on memory allocation so that javascript GC wouldn't introduce lags now and then was another 5 hours. (That is the main performance problem with non-native apps, I think.)