According to this handy bandwidth calculator (murideo.com), 10k@60 Hz/10 bits/4:4:4 requires 26.73 Gbps with DSC. Yes, DP 2.0 is 80 Gbps. But does the M1's TB4 support this? I'd be surprised. And if it doesn't, i.e., if it's limited to TB4's standard 40 Gbps, you would only be able to drive one 10k, not three.
And even with 80 Gbps you could only connect one XDR without compression (6k@60 Hz/10 bits/4:4:4 = 46.1 Gbps).
But yes, if you compressed the Pro Display XDR with DSC, that would be 12.3 Gbps/display @60 Hz/10 bits/4:4:4, so you could drive three with a single 40 Gbps TB4 cable.
Though Apple's spec's say the M1 Pro and M1 Max are limited to 2 x 6k and 3 x 6k respectively, which may be a GPU limitation.
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