Lower Third / drawbox

[Cristofayre]

Forgive this "newbie" if post format is incorrect.

I'm developing a little app that creates video captions, both SRT and SSA. (SRT as text file, and SRT/SSA as 'burned in' along the bottom of the video. The GUI version handles this well) Until this morning, I was going to use FFMPEG. Now I've discoverered the HandBrakeCLI version - which is 1/10th the size at 16KB

I can no doubt 'develop' the code to burn in the captions via trial and error, but there is one option I know FFMPEG can do, but not sure if CLI can.

There is a command called "DrawBox" that allows you to add a coloured bar the full width of the screen - a bit like a Lower Third - and the captions are printed on top of that. Is that possible? (Theoretically as HB is based on FFMPEG so I've read)

+++
Not tested, but can someone vertify if this is the correct format to burn in captions:
"-i input.mp4 -Z,--Preset Very Fast 1080p30 -N, --ssa-burn captions.ssa -o outputFile.mp4"