are you precompressing something that requires depth level to be set to 3 or higher? as for choosing between reflate or preflate, you need to know how each works as they have their advantages and disadvantages.
Code:
.\xtool.exe precomp -mzlib+reflate -d3 -c128mb -t100p-1 D:\xtool2020\test.zip output.bin
14992 streams
.\xtool.exe precomp -mzlib+preflate -d5 -c128mb -t100p-1 D:\xtool2020\test.zip output.bin
2603 streams
which should explain their differences seen here. What I would point out as the main difference, reflate supports streams with no tail while preflate doesn't so if a special deflate encoder was used or if a stream had been cut off, preflate will be unable to process such streams but reflate is able to handle these.
as for {option} via freearc, I'd first say you need to understand the command line syntax of xtool. The old xtool and new xtool use different syntax.
Code:
[External compressor:xtool]
header = 0
packcmd = xtool.exe precomp -mzlib -c32mb -t100p - - <stdin> <stdout>
Ideally this would become
Code:
[External compressor:xtool]
header = 0
packcmd = xtool.exe precomp {option} - - <stdin> <stdout>
then used as -mxtool:mzlib:c32mb:t100p from freearc.