Lockdown Mode is nice for blocking spam, and while it may have decent protection against attacks when the phone is locked as is claimed, it might be worth taking additional precautions:
* disable face ID or fingerprint unlock
* use a passcode with more than 8 characters
* enable erasing data after 10 failed attempts
* enable Advanced Data Protection, or disable iCloud backups altogether
️ I use my fingers, hand, and arm, as you said, it's more than good enough