They're not going to hold a candle to the 64Audios, though, so I hope he's ready to take a major step backwards in resolution in order to have that wireless convenience.
The TWS game, as it stands right now, is still heavily steeped in compromise. There have been a couple pairs that wowed me for how many of the boxes they can check given their price point, but I don't know if they're going to really fall within your sonic requirements. If it's purely a gym-based set, try to find pairs that favor a secure/comfortable fit; something like the Jabra Elite Active 75t (once you've swapped out the tips) or Ultimate Ears' UE FITS would be my suggested starting points, depending on which price to entry you're comfortable with.
The UEs will probably be the most CIEM-like, both in terms of relative fit and overall sound signature, even though they're only using a single dynamic driver. If you need a multi-driver setup, the options list gets narrower. Those choices include:
- Noble Falcon Pro - 1 DD, 2 Knowles BAs per ear; battery life is good, fit is wonky and driver flex becomes a real issue if pressure across both sides isn't neutral. Since there's no vent to help with this, I don't know if I'd consider them a good gym pair
- Status Between Pro - Can't speak on them any more than they're a multi-driver set like the Noble. I'll find out in April if they're worth anything
- Galaxy Buds Pro - Can't speak on these either, though seems they're mostly favorable here. Based on the shape, I'm not sure how secure they'd be long-term
It'll also depend on what you're listening to, primarily. While I can advocate for the EA75t, it's only on a limited set of genres.
For what it's worth, by the way, coming in and saying you're going to ignore 2,000 pages of time and energy people spent already answering your questions in favor of being spoon-fed is really bad practice. Take a chunk at a time if you have to, read only the last 20 pages...do whatever, but don't be rude. Meh, it's water under the bridge