Client-side a/b testing/personalizations(default option for google optimize, visual website optimizer, optimizely) mean you have to use page hiding snippet - https://support.google.com/optimize/answer/7100284?hl=en.

Which, if you look at it closer - "'dataLayer',4000," 4000 ms mean that you basicly make your website white blank for up to 4s while all the ab testing loading stuff is happening behind the scenes.

And this makes your initial load UX a very very awkward experience.

If personalization / ab testing is happining on load-time parameters (i.e. country), well, you are in a situation where I have mentioned hydrated site is out of options to be considered for the stack selection.

As for other points, let me elaborate on web analytics. Google Analytics default seup collect around 70-80% of transactions/events/pageviews data. If you want to fix this, you revert to server-side stuff, and that's where you meet js-based navigations.

That's when you either try to go this way with gatsby: https://www.gatsbyjs.com/plugins/gatsby-plugin-no-javascript... .

That's when you are stuck with sapper: https://stackoverflow.com/questions/64507516/how-to-disable-... .

That's when you end up in tickets like this with Nextjs: https://github.com/vercel/next.js/issues/4381 . And never look back.

As for pageload, next.js is 30% slower than vanilla website. No ecommerce bussiness should ever alow this(my personal opinion).

Take a look at my top comment of https://news.ycombinator.com/item?id=25342767 for more details.