Advise on where to start

New to RPIs and Linux. I am running a dashboard in A truck that is running TunerStudio EFI tuning software and I have a 12.3” ultra wide screen in where my factory gauges where. I am also running a juice4hault ups to buffer when voltage drops and auto shut down the RPI. I’m currently running it on raspbian noobs install but boot up takes for ever. I am wanting to use dietpi cause it’s fast to boot. I don’t need the desktop GUI to load just want to to load the software that also requires java with no interactions and have my ups to still function also. Last thing I would like to try to get to work is some way to easily share files between laptop and RPI I’m fine with hotspotting from phones or how ever. I loaded the VM image and played with it. I was able to load tunerstudio but country figure out how to auto load it. Any place that may read up and try to figure this out would be helpful. Thank you.

Generally to auto load scripts on boot, you can put them into /var/lib/dietpi/postboot.d. Those will run after all regular services have been loaded, but before login prompt.

For interactive software that should only start on login, put a run script into /etc/profile.d/ with .sh file ending.