We should just use the books as a source. Also I'll leave this link here as I did on discord.
https://middle-earth.xenite.org/what-did-sauron-look-like/
Middle-earth Xenite is probably the best Middle-earth blog out there, so it's totally reliable and worth reading. I think the books say that Sauron's 'spiritual form' was an Eye, or a wheel of fire as Frodo (almost half a ring-wraith at the time) describes it. Also it's used by Mordor as emblem, like when the Orcs painted it on the statue in Ithilien. I think it's quite clear the books say Sauron
did have a physical form, and not that of an Eye. After Sauron's fair body that he used to corrupt the Númenoreans in the end of the Second Age was destroyed, he could no longer take fair shapes. That was a big loss for him, because especially in his early days, shape-taking was his specialty. This doesn't mean that he couldn't take body forms anymore, of course not: he had a body during the Last Alliance. But the books provide proof that also after Isildur cut off his finger, Sauron took a physical body. When Gollum described his tortures in Mordor, he describes Sauron having four fingers. This has to be the physical embodiment of Sauron, and not that of an eye. So I'm convinced that Tolkien thought of Sauron having a body.
I actually like Red's idea of choosing and I think it is possible, and we could even extend the eye a bit above the height limit. I remember
@q220 testing the holograms plugin a few years ago, I think it's this plugin:
Holographic Displays. He even tested it with an image of the Eye (coincidence? I think not). This could easily be switched off and on by preference and might be the best solution? One problem would be that the holograms would rotate with your point of view. The holograms are actually nametags of invisible entities I think, and nametags rotate along with you. Maybe this could be fixed by dividing the eye in a lot of different hologram though.