Maybe a better term instead of "centralized vs. decentralized" would be "self-custodial vs. non-custodial".
"Self-custodial" would mean that you'll own your private keys, while "non-custodial" would mean that someone else except you is managing the private keys for you and you are not owning these private keys. Classical "not your keys - not your coins".

The term "centralized vs. decentralized" is better suitable for a comparison between Uniswap (Decentralized exchange) and Coinbase (Centralized exchange).

While open source (code is publicly available) isn't directly related to "self-custodial vs. non-custodial", there are still wallets where:
1.) you'll own your private keys but the wallet is not open source (Exodus wallet) = self-custodial + closed source
2.) you'll own your private keys and the wallet is open source (Electrum wallet) = self-custodial + open source

While I would go for 2.), point 1.) is still by far better than a centralized exchange, where you don't own your private key.
But 2.) is clearly my choice and all Blockchain experts will agree here.