I created my own style and made the text smaller and almost transparent. I can still see the text, but the subtitles don’t block the scene.
Bit of a learning curve, but that's what I finally ended up doing myself. For anyone reading, creating our own style actually means adapting whichever existing style you last clicked, to format a new one, at Apple Menu -> System Settings -> Accessibility -> Captions. Click an existing style, then "+". Choose your options. I decreased the default size to Medium and chose Semitransparent. Good luck!