Why copied fancy text is different from a font
Fancy text replaces ordinary letters with Unicode characters. It does not install a font, so the copied characters can look or behave differently in another app.
Choose the result for the place it will be used
Type your text in the font generator, filter by a style name and copy its row. Paste it into the destination before committing to it. Missing boxes or a different appearance mean the destination is not showing that character as expected.
For important instructions, names that must be searched or text read aloud by software, keep an ordinary-text version. The decorative characters are not the same stored letters as the original.
Small text and glitch text change different things
Small caps and tiny superscript use the characters available in the supplied mappings. A letter with no counterpart stays unchanged, so a style need not transform every character.
Glitch text adds combining marks. The character counter can show why the copied result has more code points than visible characters. A receiving form may count either of those or bytes.
Use ordinary case when that is all you need
Uppercase and lowercase conversion changes letter case. Use the case converter for that job; replacing a letter with a decorative symbol is a different transformation.