The block editor is a powerful tool, but also one that can cause you a lot of harm if you don't know how to use it properly.
Generally, we do not recommend making styling changes to individual blocks.
With very few exceptions, everybody designs and writes their post on a desktop device.
However, 80% of your pageviews come from Mobile devices.
This means that any changes you're making should be done for the benefit of mobile devices.
A component of branding is consistency: people expect that pages on a site look more or less the same.
If one page has headings with underlines, and another has headings with all uppercase, and another page has headings in the color teal, the user may assume they've been sent to a third party site.
While this is less significant of a factor with proper optimization (eg. WP Rocket with Critical CSS), adding styles to a page can increase browser rendering time.
Changing styling on a post-by-post basis not only creates inconsistent branding, it also makes maintenance a nightmare. If you set a color that doens't meet accessibility contrast standards and have to update it a year later, you have to manually edit every page you've done this on.
For a site with hundreds of posts, this is a huge task.
The correct way to do this is to edit styling site-wide via "Additional CSS" or in the code snippets plugin. See this article on the types of customizations.
Return on investment
You can, and should, customize your site if there's a compelling reason for it. See: why am I making this change.
What's your expected return on investment for making this change on this specific page? Is it going to increase your overall income 1%? 10%?
Pagebuilders and modifying styling on a block-by-block and page-by-page basis has one admittedly useful market: marketing/ad agencies that churn out hundreds of landing pages each month for A/B testing purposes.
To this segment of the market, a 1% lift in conversion could be worth thousands of dollars per year.
To a recipe site that relies on ad revenue? Not so much.
Note: if run ads for a landing pages for offer services such as:
- cooking classes
- food photography for restaurants
- personal chef services
- nutrition counselling
You may benefit from running A/B tests like this, if you have enough volume on those pages to get statistically significant results.