I'm not familiar with GeoJSON, but here's how you can work with it using the Google Maps v3 API:

For a single marker:

        lng = (4.502384184313996, 4.461185453845246);
        lat = (51.011527400014664, 51.02974935275779);
        cur_loc = new google.maps.LatLng(lat, lng);

        var marker = new google.maps.Marker({
            position: cur_loc, 
            draggable: false,
            animation: google.maps.Animation.DROP,
            icon: image
        });

        // Use setMap() to add the marker to the map;
        marker.setMap(map);

For multiple markers retrieved from MySQL (via Ajax):

        google.maps.event.addListener(map, 'idle', function () {
            var bounds = map.getBounds();
            var ne_lat = bounds.getNorthEast().lat();
            var ne_lng = bounds.getNorthEast().lng();
            var sw_lat = bounds.getSouthWest().lat();
            var sw_lng = bounds.getSouthWest().lng();
            // Make an Ajax call to your server passing the bounds
            $.ajax({
                  type: "GET",
                  url: "http://www.zwoop.be/develop/home/bars/bars_get_markers.php",
                  data: {
                      'ne_lat': ne_lat,
                      'ne_lng': ne_lng,
                      'sw_lat': sw_lat, 
                      'sw_lng': sw_lng
                  },
                  datatype: "json",
                  success: function(data){
                    if(data){
                        // Remove current markers and add new ones in the Ajax callback
                        function clearOverlays() {
                            for (var i = 0; i < array_markers.length; i++ ){
                                array_markers[i].setMap(null);
                            }
                            array_markers = [];
                        };
                        clearOverlays();

                        // Parse the returned JSON object
                        // Create a marker for each object                        
                        var obj  = $.parseJSON(data);
                        $.each(obj, function(index,el) {
                            var bar_position = new google.maps.LatLng(el.lat, el.lng);
                            image_bar = "http://www.sherv.net/cm/emoticons/drink/whiskey-smiley-emoticon.gif";

                            var marker = new google.maps.Marker({
                                position: bar_position,
                                map: map, 
                                icon: image_bar
                                });
                            // Add info window that can be edited with HTML content
                            google.maps.event.addListener(marker, 'click', function() {
                                if (infowindow){
                                    infowindow.close();
                                };
                                content = "<div id='infowindow_container'><h3><a class='profile_name_bar' href='#' id='" + el.profile_id + "'>"+el.profile_name+"</a></h3></div>";
                                infowindow = new google.maps.InfoWindow({ 
                                    content: content
                                });
                                infowindow.open(map,marker);
                            });                            
                            array_markers.push(marker);
                        });

                        // Place the markers on the map
                        function setAllMap(map) {
                          for (var i = 0; i < array_markers.length; i++) {
                            array_markers[i].setMap(map);
                          }
                        }
                        setAllMap(map);

                        // Utilize marker clusterer to avoid overcrowded markers
                        var zoom = 17;
                        var size = size ==-1?null:size;
                        var style = style ==-1?null:style;
                        var markerCluster = new MarkerClusterer(map, array_markers,{maxZoom:zoom,gridSize:size});
                    }
                },
                  error: function (xhr, ajaxOptions, error) {
                        alert(error);
                        }
                    })             
          });

This code loads markers dynamically based on the map viewport. As you zoom or pan, it queries the database to fetch marker coordinates within the map bounds via Ajax. These coordinates are then displayed on the map after being stored in an array client-side. I included the marker clusterer feature to handle clustered markers effectively.

I hope this information is helpful. Unfortunately, I'm not aware of the advantages of the plugin you're using.

I'm currently working on a similar project, and here's where I stand at the moment.

My approach involves utilizing PHP to retrieve coordinates from a MySQL database and generating a GeoJSON object like this:

var geoJson = [
    {
        type: 'Feature',
        "geometry": { "type": "Point", "coordinates": [-77.03, 38.90]},
        "properties": {}
    },
    {
       type: 'Feature',
       "geometry": { "type": "Point", "coordinates": [-64.567, 32.483]},
       "properties": {}
    }      
];

Here is a snippet of the PHP code I am using:

<?php  
            // Establish Connection
            $link = mysqli_connect("[host]","[username]","[password]","[database-name]") or die("Error " . mysqli_error($link));

            // Retrieve place coordinates
            $query = "SELECT * FROM `places`";
            $places = $link->query($query);

                var geoJson  = [<?php

                // Iterate through places and construct JSON data

                $i = 1;
                while($venue = $venues->fetch_assoc()): 

                    if($i > 1){ echo ","; } ?>
                    {
                        type: 'Feature',
                        "geometry": { "type": "Point", "coordinates": [<?php echo $venue['lon']; ?>, <?php echo $venue['lat']; ?>]},
                        "properties": {}
                    }

                    <?php $i++; ?>

                <?php endwhile; ?>

            ];




            map.markerLayer.setGeoJSON(geoJson);

Please note that this PHP code is integrated within the JavaScript for handling the map functionality.

Although the current implementation fulfills its purpose, I am considering exploring JavaScript templates as an alternative method of fetching and presenting the data. Perhaps this could offer a more efficient solution. Feel free to reach out if you make further progress on this front :)