＞Cubaseは切ったらむしろ減る
って、もしトータルで考えてるとしたらHTの影響がどこに出るかよくわかってないと思う

1コアを有効に使うための作業が余計に入るから〜ってところが影響するわけで
Steinbergもリアルタイムで低レイテンシーを求める場合にはオフを推奨してる
https://helpcenter.steinberg.de/hc/en-us/articles/206625630-Hyperthreading-Simultaneous-Multithreading-and-ASIO-Guard
Enabling SMT/"Hyperthreading" while ASIO Guard is active usually has a positive effect on the overall system performance and is the recommended combination.
Only in rare cases - e.g. with projects using many "live" tracks - SMT can still lead to performance issues. Again,
please refer to the dedicated ASIO Guard article for details.