I think their goal is for Grafana to be the abstraction layer for every datastore. You just hook up their specialized cloud hosted datastore for each type of data and then plugin Grafana and don't even think about it much.

Basically they are churning out all these different projects that just need to be "good enough" from a performance perspective

I have used Grafana in conjunction with Influxdb (1.x & 2.x), postgresql, mssql and mariadb with little issue for ~5 years. I have not dipped my toes in the water experimenting with the log aggregators. Some of the 3rd party plugins have been difficult to use and there are some odd bugs here and there (histograms on older versions finding the proper xmin and xmax). What specifically has been confusing?

I just checked their website and they have 4 products listed under "Products"...

Grafana is obviously the main one, their original product and the most popular one. It's to aggregate data from various sources and make dashboards.

Loki is a logs collector that I personally didn't try but I think it's popular. They released it after Grafana.

I don't know the third one.

The last one seems to be a wrapper around Prometheus (a metrics collector/database).

Fair to assume you should start with Grafana. For the source, if you don't have a Prometheus instance, you can test it with any SQL database.