Yes. You can withdraw from your vault or Trade wallet to any bitcoin address you choose, including your own hardware wallet. Onramp charges no withdrawal fee, only the bitcoin network fee.
Vault withdrawals go through identity verification and video calls with Onramp and BitGo, and most take 24 to 48 hours. Trade wallet withdrawals only need a video call the first time you send to a new address, or for more than $5,000,000 in 24 hours.