It's mainly electron, but I'll look in the future to cut down the size.
(My Budget author here).
You might be interested in Proton Native (https://proton-native.js.org/#/) which should produce a much more lightweight output and has native controls. I have not used it though so I cannot vouch for whether it is sufficient for your needs.
I'd have to see if it has all the building/signing and packaging support as electron. Thanks for linking!