Not sure if the numbers after LZMS: do anything in that case.
Also, as far as I know, neither Winre.wim nor boot.wim supports solid format, but will it have compatibility issues with non-solid LZMS compression with custom chunk size?
I think this is one of the cases that's still limited to LZX 32K as the best available compression method, but this is a limitation in Microsoft software that I don't have insight into. Try it and see if it works with the particular Windows version you're using.
Thank you for your reply, I appreciate it. I'll look into it if I have some spare time. For now, I've tried doing LZX:100 (the default chunk size) with Windows 10 21H2 ISO for both boot.wim and Winre.wim, and it seems to work.