I want to transfer my device to a new account. Will the data from the device (the target device) be lost or be transferred to a new account?

No, your recorded/tracked data will not be lost.

All recorded data will be transferred to a new account with your device. To transfer your device to a new account, open the TheTruthSpy interface on the target phone, then log in with a new account. Your device with all recorded data will be transferred to a new account.