Yes, priority for AVG and weight for AVF.
Priority determines which router functions as AVG (this is the router that will reply to ARP requests for clients on the subnet, passing out a MAC for the AVF routers to each client).
Weighting determines the proportional distribution of MACs from the AVF routers to client host responses. If two AVF routers are equal weight, the AVG will distribute their MACs equally in response to client ARP requests.
In your configuration, R1 has highest priority and will function as AVG.
If you want to avoid R2 as a forwarder unless R1 is down, you should consider using HSRP instead of GLBP, or use GLBP without load balancing:
no glbp 1 load-balancing
Given the weighting defined in your config on R1 and R2, the weight for R1 is set as 254 and tracking object 10. If object 10 fails, the weighting threshold is decremented 250, which drops below your defined lower threshold of 10, triggering R1 to stop acting as an AVF.