@amd, a few answers:
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You have something close to a parallel feed, but your branch doesn’t happen until after the big 400A breaker, based on what you have described. I have a true parallel feed, that doesn’t let me put CTs around the combined split output of the meter (so my CTs on the 2 single main buses before the meter).
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You can clip multiple wires within a CT as long as the current flow direction and phase are the same. In your configuration, that is absolutely true. The red tape at the bottom distinguishes one phase from the other.
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With no solar, you could get a second sensor and do the split 200A approach. Unless you are actually using more than 200A at any one time, that approach probably won’t improve things, and will preclude monitoring Solar or a generator in the future. If you do have regular usage over 200A (for the whole house), then Sense might show clipping where the monitored current/power flattens out because the measurements are out of the calibrated range.