Example

$form = new Form('plugins-nice-check-form-1', 'horizontal');

$form->addRadio('vertical-radio', 'One', 1);
$form->addRadio('vertical-radio', 'Two', 2, 'checked');
$form->printRadioGroup('vertical-radio', 'Vertical radio buttons', false);

$form->addCheckbox('vertical-checkbox', 'First', 1);
$form->addCheckbox('vertical-checkbox', 'Second', 2, 'checked');
$form->addCheckbox('vertical-checkbox', 'Third', 3);
$form->printCheckboxGroup('vertical-checkbox', 'Vertical checkboxes', false);

$form->addRadio('horizontal-radio', 'One', 1, 'checked');
$form->addRadio('horizontal-radio', 'Two', 2, 'checked');
$form->printRadioGroup('horizontal-radio', 'horizontal radio buttons', true);

$form->addCheckbox('horizontal-checkbox', 'First', 1);
$form->addCheckbox('horizontal-checkbox', 'Second', 2);
$form->addCheckbox('horizontal-checkbox', 'Third', 3, 'checked');
$form->printCheckboxGroup('horizontal-checkbox', 'Horizontal checkboxes', true);

$form->addPlugin('nice-check', '#plugins-nice-check-form-1', 'default', ['skin' => 'red']);
<div class="row">
    <label class="main-label col-sm-4 col-form-label">Vertical radio buttons</label>
    <div class="col-sm-8 mb-3">
        <div class="form-check">
            <input type="radio" id="vertical-radio_0" name="vertical-radio" value="1" class="form-check-input">
            <label for="vertical-radio_0" class="form-label">One</label>
        </div>
        <div class="form-check">
            <input type="radio" id="vertical-radio_1" name="vertical-radio" value="2" checked class="form-check-input">
            <label for="vertical-radio_1" class="form-label">Two</label>
        </div>
    </div>
</div>
<div class="row">
    <label class="main-label col-sm-4 col-form-label">Vertical checkboxes</label>
    <div class="col-sm-8 mb-3">
        <div class="form-check">
            <input type="checkbox" id="vertical-checkbox_0" name="vertical-checkbox[]" value="1" class="form-check-input">
            <label for="vertical-checkbox_0" class="form-label">First</label>
        </div>
        <div class="form-check">
            <input type="checkbox" id="vertical-checkbox_1" name="vertical-checkbox[]" value="2" checked class="form-check-input">
            <label for="vertical-checkbox_1" class="form-label">Second</label>
        </div>
        <div class="form-check">
            <input type="checkbox" id="vertical-checkbox_2" name="vertical-checkbox[]" value="3" class="form-check-input">
            <label for="vertical-checkbox_2" class="form-label">Third</label>
        </div>
    </div>
</div>
<div class="row">
    <label class="main-label main-label-inline col-sm-4 col-form-label">horizontal radio buttons</label>
    <div class="col-sm-8 mb-3">
        <div class="form-check form-check-inline">
            <input type="radio" id="horizontal-radio_0" name="horizontal-radio" value="1" checked class="form-check-input">
            <label for="horizontal-radio_0" class="form-check-label">One</label>
        </div>
        <div class="form-check form-check-inline">
            <input type="radio" id="horizontal-radio_1" name="horizontal-radio" value="2" checked class="form-check-input">
            <label for="horizontal-radio_1" class="form-check-label">Two</label>
        </div>
    </div>
</div>
<div class="row">
    <label class="main-label main-label-inline col-sm-4 col-form-label">Horizontal checkboxes</label>
    <div class="col-sm-8 mb-3">
        <div class="form-check form-check-inline">
            <input type="checkbox" id="horizontal-checkbox_0" name="horizontal-checkbox[]" value="1" class="form-check-input">
            <label for="horizontal-checkbox_0" class="form-check-label">First</label>
        </div>
        <div class="form-check form-check-inline">
            <input type="checkbox" id="horizontal-checkbox_1" name="horizontal-checkbox[]" value="2" class="form-check-input">
            <label for="horizontal-checkbox_1" class="form-check-label">Second</label>
        </div>
        <div class="form-check form-check-inline">
            <input type="checkbox" id="horizontal-checkbox_2" name="horizontal-checkbox[]" value="3" checked class="form-check-input">
            <label for="horizontal-checkbox_2" class="form-check-label">Third</label>
        </div>
    </div>
</div>