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I found a way to change the text through theme files but it is very basic

If you’re handy with developing, I’d recommend creating a child theme to change the text. You can change the colors, add features, etc:
https://developer.www.ads-software.com/themes/advanced-topics/child-themes/

2. To decrease space, add this via Additional CSS (or via your child theme) :

#secondary .widget {
    padding-bottom: 30px;
}

It’s 60px by default, so adjust as you like.

3. Figcaptions are controlled with CSS, too. This is a bit wild, but you get the idea of what you can do.

.wp-block-image figcaption, [class^=wp-block-] figcaption {
    font-size: 2em;
    color: pink !important;
    font-style: normal;
    text-transform: caps;
}