FFMPEG reducing Generation Loss when inserting many videos into another video - audio

Question

I am trying to insert many miniclips.mp4 into a main.mp4 video - Although I have been able to do this using this solution, I seem to suffer from Generation Loss
The command I am using (within a python script, in a loop at many different intervals) is:
ffmpeg -i main.mp4 -i miniclipX.mp4 -filter_complex "[0:v]drawbox=t=fill:enable='between(t,5,6.4)'[bg];[1:v]setpts=PTS+5/TB[fg];[bg][fg]overlay=x=(W-w)/2:y=(H-h)/2:eof_action=pass;[1:a]adelay=5s:all=1[a1];[0:a][a1]amix" output.mp4
(Then renaming output.mp4 to main.mp4 within a loop)
Would there be anyway to either:
A) Reduce generation loss by implementing certain flags
or
B) Include many different input files and many different -filter_complex's in a singular command to achieve what I am after?

Answer 1

Because you did not provide the ffmpeg log (and therefore there is no info about your ffmpeg or your inputs), for this answer I'll assume all videos are the same width and height.
Example to show miniclip1.mp4 at 5 seconds and miniclip2.mp4 at 10 seconds:
ffmpeg -i main.mp4 -i miniclip1.mp4 -i miniclip2.mp4 -filter_complex
"[1:v]setpts=PTS+5/TB[offset1];[0:v][offset1]overlay=x=(W-w)/2:y=(H-h)/2:eof_action=pass[bg];
[2:v]setpts=PTS+10/TB[offset2];[bg][offset2]overlay=x=(W-w)/2:y=(H-h)/2:eof_action=pass;
[1:a]adelay=5s:all=1[a1];
[2:a]adelay=10s:all=1[a2];
[0:a][a1][a2]amix=inputs=3"
output.mp4
Command was broken into multiple lines so it is easier to read. Make it one line when executing.