method VS timber

Here's the theme I maintain that sounds to be what you're looking for. It has the latest 5 beta included. You'll need to compile the theme.scss file, which imports Bootstrap's source scss files (so you retain access to all of Bootstrap's variables, can easily override them). I made a toolto create a custom build of the theme with the correct browser prefixes, etc. The theme's wiki is still being built, but has a lot of documentation allready in place. Right now, all frontend markup goes in the custom layout class, but thats being opened up soon.

Use Timber for templating https://github.com/timber/timber

I’ve used timber and then built of their example theme. I can share a skeleton example of my base theme that incorporates vue and vite if you’re interested!

Would just drop underscore and go for https://github.com/timber/timber with their starter theme.

Finally, since Wordpress by default doesn't have a templating language you might be annoyed by mixing HTML/PHP for templates at first. I could recommend Timber to add Twig template support to your theme. It's helped me out a great deal in cleaning up messy intermixed presentation files.

Timber or Sage as you prefer !

ACF let you make all your custom fields and assign them literally anywhere. Timber brings Twig to Wordpress so you can have your views in twig files and your logic on php files and have a neat, modular, tidy, mantainable theme without having to deal with those mixed php/html nightmares you usually see.

Ya know, one more thing you might want to just look through: Timber/Timber.

Your best bet are starter themes using the Twig templating language which is similar to the templating languages you may already know.

Timber : https://timber.github.io/docs/