Benchmarking is a mess everywhere. Sure you can get some level of accuracy but reproducing any kind of benchmark results across machines is impossible. That's why perf people focus on things like CPU cycles, heap size, cache access etc instead of time. Even with multiple runs and averaged out results you can only get a surface level idea of how your code is actually performing.
React is not slow. React is not "big". React is not the reason your website is slow.
Any engineer who thinks that its React that is causing the slow renders and replacing it with X is deluded. Yes, there are ways to make slow React web apps. But there are also ways to make fast React web apps. It just requires effort and a little bit of foresight.
You'd already be using source maps in any real-world scenario so I am not sure what's the value proposition here outside of "just for fun, I guess".
The tsc transpilation to lower ES versions is actually really useful when using not-so-recent Node versions. Not to mention this severely restricts TypeScript syntax to "just types" which isn't too bad but it means you now have to worry about yet another thing.
Then there's the ESM & CJS mess. You almost always want to export in both formats which will change a lot of the syntax, so this quickly falls apart for anything serious.
Our goal with Notesnook has always been to make privacy simpler to adopt for normal users who don't have time to think about privacy. We do that by making privacy that "default" everywhere in the app. We recently crossed 100K registered users with over 4 million notes created on our platform.
If anyone has any questions I'd be happy to answer.