So, I am assuming you want to have X-axis as _time and y axis as average CPU credit balance.
What time granularity do you want? (Use timechart span=XX where XX is the granularity (1m, 1h, 15m etc)
If you want to show the legend as the type/instance id then just create a new field like this
| eval name=instance_type.":".metric_dimensions
and use name as the split by field. instance_type will be the field that defines your instance type
No. I didn't get answer