Gravity Forms has been my contact form builder of choice for years now and the 2.5 release brings a very welcome refresh to the UI. This makes it feel more like Gutenberg and adds a lot of layout customization options to the builder that were not available before without custom coding.

CSS Code for Gravity Forms: https://github.com/permaslug/Gravity-Forms-CSS/blob/master/Base%20Code

/*** MAIN WRAPPER ***/
.gform_wrapper {

}

/*** FIELD STYLING ***/
.gform_wrapper ul.gform_fields li.gfield,
.gform_wrapper .top_label li.gfield.gf_right_half {
    padding-right: 0;
}



input[type=text], textarea, input[type=password], [type="search"], [type="date"], [type="tel"], [type="email"] {
    background: #ffffff;
    border: solid 1px rgba(225,225,225,0.85);
    border-radius: 0;
    color: #4d4d4d !important;
    font-weight: 400 !important;
    padding: 15px 12px !important;
  	font: inherit; 
}



.gform_wrapper .gform_body .gform_fields .gfield select {
    background: #ffffff;
    border: solid 1px rgba(225,225,225,0.85);
    border-radius: 0;
    color: #4d4d4d !important;
    font-weight: 700 !important;
    letter-spacing: 1px !important;
    padding: 17px 15px !important;
}


/*** FIELD FOCUS STYLING ***/

input:focus,
input[type=text]:focus,
input.text:focus,
input.title:focus,
textarea:focus {
    box-shadow: 0 10px 20px 0 rgba(0, 0, 0, .2);
    border: solid 1px rgba(225,225,225,0.75);
}

/*** MESSAGE BOX TRANSITION ***/
.gform_wrapper textarea.medium {
    margin-top: 6px;
    height: 10em;
    transition: height .3s ease-out;
}

/*** MESSAGE BOX FOCUS HEIGHT ***/
.gform_wrapper textarea.medium:focus {
    height: 25em;
}

/*** BUTTON STYLING ***/
.gform_wrapper .gform_footer input.button,
.gform_wrapper .gform_footer input[type=submit] {

  
}

.gform_wrapper input[type=submit] {
    cursor: pointer;
    text-transform: capitalize;
    font: inherit;
    font-weight: 300;
    padding: 12px 25px;
    width: 150px;
    border-radius: 0;
    background: #137d7d;
    color: #f7f7f7;
    text-transform: uppercase;
    letter-spacing: 1px;
    border: none;
  	border-radius: 3px;
    transition: box-shadow .2s ease-in-out;
}

/*** BUTTON HOVER STYLING ***/
.gform_wrapper input[type=submit]:hover {
    background: #004D4D;
    color: #fff;
    box-shadow: 0 10px 20px 0 rgba(0, 0, 0, 0.2);
}

.gform_wrapper .gform_body .gform_page_footer .gform_next_button {
    cursor: pointer;
    text-transform: capitalize;
    font-weight: 300;
    padding: 10px 12px;
    border-radius: 0;
    background: #137d7d;
    color: #f7f7f7;
    border: none;
  	border-radius: 3px;
    transition: box-shadow .2s ease-in-out;
}

.gform_wrapper .gform_body .gform_page_footer .gform_next_button:hover {
    background: #004D4D;
    color: #fff;
    box-shadow: 0 5px 10px 0 rgba(0, 0, 0, .2);
}

.gform_wrapper .gf_progressbar_wrapper .gf_progressbar .gf_progressbar_percentage {
  background-color: #43b5ac;
}