The foundation.
WHY IT MATTERS
Some themes load enormous amounts of code on every page regardless of what you use.
A heavy theme puts a floor under how fast your site can be.
WHAT MAKES A THEME SLOW
Loading every feature whether used or not Bundled sliders and page builders Large icon and font libraries Many separate script and style files
WHAT TO LOOK FOR
Simplicity A small default page weight Good reviews mentioning performance Active maintenance
HOW TO CHECK BEFORE COMMITTING
Run a speed test on the theme's demo site.
That tells you the floor before you add your own content.
THE PAGE BUILDER QUESTION
Builders are convenient and generally add weight.
They also make moving to another theme difficult later.
Consider that before committing.
CHANGING THEMES LATER
Disruptive. Content built with a builder may not survive.
Choose deliberately at the start.
