Why three, and why plastic
Three is the number that works: two to lift the bead over the rim and hold it there, one to run round the tyre. Two will do it on a loose tyre and leave you swearing at a tight one.
Plastic rather than steel, because a metal lever will gouge an alloy rim and can crack a carbon one — and on a tubeless setup, a scratched rim bed is a rim that will not hold air properly afterwards.
Worth keeping with a spare inner tube rather than in the toolbox at home. They are no use in the garage.
