Suggest Voyager to cover:
What is custody?
What is mining?
What is blockchain?
PoS vs PoW
Hardforks & Consensus
How is ETH different from BTC?
What are nodes? (Staking, Oracles, Watchers, ect)
ETH scaling: Layer 1 vs Layer 2
What makes other chains different? (DOT, ADA, TRON)