Menu page with three columns

Question

I would avoid any core-related layout classes and just roll your own (you don’t need bootstrap for this). In your PHP page handler, just kick out something like:

<div class="wrap">

    <div class="my-plugin-column">
       How...
    </div>

    <div class="my-plugin-column">
       you...
    </div>

    <div class="my-plugin-column">
       doin'?
    </div>

    <!-- And so forth -->

</div>

And then in your plugin CSS:

@media screen and (min-width: 40em) {
    .my-plugin-column {
        float: left;
        width: 30%;
    }

    /* first column */
    .my-plugin-column:nth-child(3n+1) {
        clear: left;
    }

    /* second and third columns */
    .my-plugin-column:nth-child(3n+2),
    .my-plugin-column:nth-child(3n+3) {
        margin-left: 5%;
    }
}

You could be even more advanced and display two columns at smaller breakpoint, before you switch to three for larger devices.