Welcome to the forum! You might get more answers to this query on the IEMs Discovery & General Discussion thread.
In my limited experience, it’s tricky trying to find an IEM that correlates to the sound of full-size headphones. There’s something of an apples-to-oranges element to the overall presentation, especially when it comes to soundstage, of course. Such qualities as frequency response and tuning, resolving ability, macrodynamics, and the like can be a better frame of reference, so it’s helpful that you described what you like and what you find less pleasing about the Clear. I’ve likewise got the Clear and an HD 800 SDR and I’ve yet to find equivalent IEMs.
In some ways, the closest to the Clear I’ve found is the Final Audio A8000. These IEMs extend well at both ends of the frequency response, and the bass is satisfying; their imaging is excellent; the soundstage is good enough, actually quite decent (for an IEM), and there’s plenty of punch and dynamism to the sound. The deal-breaking problem for me was the treble: it’s too fatiguing, and it has a kind of crystalline or hard, almost glass-like quality to it. I share your sense of slight brightness in the Clear’s treble and these Final Audio IEMs are worse in this respect. Still, I hope this is a useful data point, even if it only helps you rule out one option.
You might be better served with a Campfire Audio Solaris 2020. I found it quite aggressive - not unlike the Clear, then, in a way - but it was also too bright for my tastes. Others don’t share that opinion, though, so I’d suggest looking through the reviews on various forums. The original Solaris might be a better option for you. Its bass is excellent, it has a nice bit of sparkle in the treble, and it does have an excellent, 3D soundstage. It’s not the widest soundstage, if you prefer the spaciousness of the HD 800S over the Clear, but almost everyone calls it “holographic.” For an IEM, it’s truly impressive in this regard.
For a beautifully open, spacious soundstage - such as you can get from an IEM - the Campfire Andromedas (both the original, now aka the “2019,” and the latest version, the “2020”) are a great option. The resolution is excellent, for the price (there are better, as you’ll have seen with @jrockwell’s posts), and there’s a lovely sparkle to the treble - more so with the original, which might suit your tastes better. The snag is the bass. It’s good in its way but it lacks heft and sub-bass extension. Here the Solaris wins. But for musicality, the Andro is great. You might find the 2020 version too dark. I have it and like it as a contrast to my over-ear headphones.
One last thought: I just auditioned the Empire Ears Odin. They’re very impressive, especially in their resolving capabilities, musicality, and engaging qualities. The bass is probably the best I’ve heard with an IEM. It’s not overdone; rather, there’s a slight emphasis but the textures and heft, and the sub-bass depth, are lovely. The treble lacks that last bit of sparkle and extension but the IEMs aren’t fatiguing and, with the exception of listening to acoustic instruments, especially in classical music, I didn’t feel as though I was missing out too much.
There are always tradeoffs, and I’ve yet to find an IEM that’s close to the Clear. But I don’t have much experience with IEMs, and I’m still searching myself for something that follows your preferences. Do please let us know if you find something, I’d be keen to find out about it!