That is a great initiative, and I wish more producers release more content like this, my remark was due to expectations related to the "FOSS mixtape" title.
That said you should use what is best for your workflow (not for the sake of it being FOSS).
Although Ardour is perhaps almost there in terms of maturity, LV2 plugins (open source format) are not anywhere close. You can still use VSTs and AU in the windows/mac versions IIRC.
There is kinda community around releasing music with available session files with FOSS tools, although not many as polished as yours (see [1]).