The only subtle distinction is that to get an IR(H) you need the HPA exam because the new TK for the CB IR omits certain learning objectives considered relevant.
No. The CbM IR is not available to helicopter pilots.
In order to extend the privileges of the CbM IR to include other types or classes of
aeroplanes under IFR, the CbM IR holder will be required to pass the HPA examination.
This is not the case with the current IR(A), but is a result of the 40% reduction in theoretical knowledge requirements for the CbM IR.
Whether commercial schools will embrace the CbM IR for its prospective airline pilots, particularly if any IR training is outsourced to freelance IRIs, remains to be seen.