The top cap will control your temp in a kamado. For low and slow it will be barely open like maybe 1/2″. Finetune adjustments for slight temp changes with the bottom vent.
Dont worry about too much lump. Fill it up above the vent holes in the firebox. When you are done and shut all the vents, it will choke out. Then just remove the ash before your next cook and add some new lump. You will be amazed at how little lump you actually use.
The Captain is spot on Temp is controlled by vents and airflow, load up the coals.
One more small note, on placement of your grate. For direct grilling it can be as low as the top of the firebox where it is in your pics. For indirect it’s more typically higher at the level of where the grill opens. Then the diffuser is at the top of the firebox. true for both BGE and Kamado Joe.