I think you’re overthinking this.

You’re looking at cold start download sizes, but that’s not what people actual see after everything is cached follow the first load.

Google pages load plenty fast on every device I’ve used recently, including some very old android tablets. Most page loads don’t transfer much data at all due to caching. Combined with the high speeds of both browsers and devices today, there wouldn’t be much real change in a highly stripped down Google page relative to what they’re serving up today.