How are programs usually started in linux-based embedded systems?

Hello dear people,
I try to find out how programs are usually started in embedded Linux-based devices. In addition to own considerations and web research i wanted to resolve this as a kind of expert interview to interview Linux experts. Maybe you can help me?

The idea is to find the actually running programs statically in the file system or dynamically with tools. Therefore, I have to know in which ways these are started after booting. Of course, I have already done my first research. Please correct me:

1.) Directly at / after booting: You adapt your own init start program, in which you start external programs. (Is this realistic?)

2.) Autostart function of the respective distribution, usually in a special config file. Unfortunately very distribution specific. Example gnome-sessionproperties (Ubuntu, Mint) ... rc.local unter Debian... My question: Are there other standardized ways, especially in the embedded environment?

3.) bashrc, is a configuration file of the bash, Entries are executed when the terminal is called. Since bash is under many Linux systems the standard shell, it is possibly a solution. However, the terminal must first be called, which does not happen automatically at system startup.

4.)cron jobs.

How is this usually done in embedded systems? Are there other ways that are possible? Many many thanks