I don’t really see how a theme can speed up a website. There are a lot of aspects to look into a website speed, a theme itself don’t really make a lot of different.
When Gutenberg was first introduced, it was a big hit with all the tutorials and shit. Then now with Full Site Editor using the exact same thing, there are still tons of tutorials (not those tips and tricks workaround and stuff) on how to use Gutenberg. Maybe Gutenberg itself is not user friendly enough.
The website is going to be running your business 24/7, get a decent hosting package, don’t get the cheapest one on the list. Trust me, WordPress is a resources monster, the cheapest one don’t work. Your business should be decent or better, at least get a decent host.
WordPress is a product built for mass market, hence it will load a lot of stuff even if the resources aren’t used by your website. So by default, you cannot really get 100% score on web metric site. However, adding plugins will also bring down the score too. It’s just egg and chicken situation, relax a bit on metric, get a score that pass like in high school but built your content instead.
WordPress usual import/export tools works better than Elementor import/export kit. WordPress export and import everything on the site. If you’re serious about changing domain/backup, go with WordPress usual route, everything in Elementor will be imported just as Elementor import/export kit does. Elementor just package a very nice name that do pages and its own templates only.
Get a good hosting service, remove the unused, complex plugins are the both most basic and essential WordPress tips.
Can’t do much on this builder. Why not just use the common Gutenberg editor with the help of widgets instead? Widgets are so useful, yet when it comes to header and footer, it’s limited.