As you mentioned, since this is just for personal home viewing, the only restrictions on your final delivery specs would be what your display and playback devices can handle.
I would consider finishing in the 2.40:1 aspect ratio. It’s visually indistinguishable from 2.39:1, and since you’ll be working with even integers for your pixel dimensions, it should scale with better quality.
If that sounds good, then I would consider setting up your project as 2592x1080. This would allow you to reframe in the horizontal dimension, while keeping the full vertical resolution. Then when you export, you can always set the frame size to 1920x1080 with a letterbox to burn to Blu-Ray disc. Or 1920x800 if you don’t want black bars for sharing online. Or export at full res for your master, and render scaled versions from that in something like Adobe Media Encoder.
The only reason I can think of for why you might want to edit with a lower res project is if your computer can’t playback smoothly at the higher res. In that case, you can always edit in 1920x800 and change the project size back to 2592x1080 before exporting. You’d just want to check any re-framing or key-framed power windows afterward to make sure they didn’t get messed up before hitting the Render button.