you will be fine on charcoal justg use about 10-12 jlit coals to start it....4.5 butt can be quicker if you foil...may be a tad longer if you dont.
Pull it from the smoker and wrap it tight with a towel it will stay warm on the counter for hours.
I like to let butts rest wrapped in foil & towels in a cooler for at the very least 1 hour. Longer is better. I have held them in a cooler for 5 hours & they were still to hot to handle with bare hands.
do I fill the basket to the brim, half-full, 3/4 full or does it not matter?