1. I don't know; I've only done it one way. I cut out most of the bottom, leaving "tabs" that I bent back towards the inside. I use the tabs to support a 12" SS pot lid that acts as diffuser/drip pan. Note: I've only used this setup once and don't have it tweaked yet. I need to add bolts/nuts as standoffs to raise the lid a little, since the support "tabs" it sits on aren't high enough to prevent the pot lid from resting on a full load of coals.
2. My clay dish sat on the tabs I described. It cracked after a few uses. It's my understand clay trays will all eventually crack, especially if you ever want the machine to be useful for high indirect heat cooks.
3. I use a large tuna can, with holes cut into its sides all around. I used one of those punch can openers like for the old metal Hi-C cans or an old metal oil can. If you're under like 40 or 50 years old you have no idea what I'm talking about. I have expanded steel tied around the charcoal grate.
The machine runs at about 230-250, both vents open, for a few hours before slowly dying down.