As has been said above, all modern Macs with either M1 or T2 already have their drives encrypted. On the Intel Macs with T2 you can still set a firmware password to prevent target disk mode with file vault turned off. On the M1 Macs, there is no firmware password and FileVault must be enabled to prevent target disk mode from being accessed.
For remote access, the T2 Intel Macs were ideal, because with a firmware password set, target disk mode could not be used to steal data, but access to the system would still be available remotely after a reboot with FileVault turned off.
Unfortunately, the M1 Macs no longer have a firmware password, so FileVault must be turned on to prevent access to target disk mode - which also has the negative side effect of needing to login at the keyboard after a reboot making remote access a bigger challenge.