You have figured out most of the diference but here you go:
#Limited - QFX 5e Series Switch - Secure Boot:
The “Junos Limited” image does not have data-plane encryption and is intended only for countries in the Eurasian Customs Union because these countries have import restrictions on software containing data plane encryption. Unlike the “Junos Worldwide” image, the “Junos Limited” image supports control plane encryption through Secure Shell (SSH) and Secure Sockets Layer (SSL), thus allowing secure management of the system.
#QFX 5e Series Switch with Enhanced Automation - Secure Boot
This software bundle is identical to the other software bundle except that Veriexec is disabled, which enables you to run unsigned programs, such as programs that you develop with Python, Chef, and Puppet.
#QFX 5e Series Switch - Secure Boot
This is the normal Junos version which you can use. It doesn't allow you to run abovementioned unsigned programs.
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"A significant system security enhancement: Secure Boot. The Secure Boot implementation is based on the UEFI 2.4 standard. The BIOS has been hardened and serves as a core root of trust. The BIOS updates, the bootloader, and the kernel are cryptographically protected. Secure boot is enabled by default on supported platforms."
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