Hello,
You have no effect because that form is not for the header builder element. Header builder elements are located at XStore core plugin.
1) To disable categories go to Theme Options > Header builder > edit search element and disable Search by category https://gyazo.com/09eaad53f4f2aca5d2aa27c0eca33c75
2) Add the following code to Theme Options > Custom CSS to get search title instead of the icon
.et_b_header-search.et_element-top-level .input-row .search-button:before {
content: 'Search';
padding: 0 20px;
}
.et_b_header-search.et_element-top-level .search-button svg {
display: none;
}
.et_b_header-search.et_element-top-level .search-button {
width: auto;
}
Regards