A quick-reference card: Bitcoin and Ethereum
Bitcoin launched in 2009, originally designed as a peer-to-peer electronic cash system, with deliberately limited scripting capabilities.
Bitcoin uses the UTXO model for accounting, while Ethereum uses the account model; the two accounting methods are different.
You need some ETH to pay gas fees when using Ethereum; Bitcoin transaction fees are paid in BTC.
$BTC and $ETH are the native coins of Bitcoin and Ethereum, respectively, and their design goals are not the same.

Just some thoughts—how you do it is up to you.