Is it possible to write a custom text on Google Maps API v3 next to the marker, or I can use only the info window to do that?
To add custom text to google maps, you can use a marker with an empty pixel for the icon:
new google.maps.Marker({
position: { lat: 0, lng: 0 },
map: map,
icon: '../res/img/empty.png',
label: {
color: '#FF0000',
fontWeight: 'bold',
text: 'Hello World',
fontSize: '20px',
},
});
Style options are listed here