Two general questions

Can all group markers be made visible on map load?

Can we make the cluster image—currently yellow and blue when a bunch of icons show up in one place on the map—made all the same color or just show the icons, even if they are crowded?

Hi.
Yes. Set it active in group list in placemark group details

As for second question - if you want to use your placemark icon as a cluster image - you can do that.
joomla.zhuk.cc/index.php/zhgooglemap-demo-clusters
It can be done - set on map details tab "Group placemarks in cluster by placemark group property" to yes, in this case icon of group will be icon of cluster

Dima,

First Item - I cannot find that setting when I edit map > Placemark Groups

Second - Cannot find it either when I edit map > Map Details tab

Hi.

No.
1 - Go to Placemark Group list, open details for each group and set it.
2 - Open map details, Placemarks tab, set to yes property "Group placemarks in cluster by placemark group property"