Z80 instability in 2 MHz FAST mode

Does it matter if you run IM1 or IM2? (doesn't seem logical, but maybe)

(I understand IM2 force the interrupt where you want it, not needing memory in page0, but is this faster or slower?)
With IM1 you must configure the RST 7 / RST 38h vector in page0 of bank1 (with moved P0 ptr) or bank0-with-preconfigure ROM
bank0: you get the Z80 ROM IM1 configured for FDFD, You bank1 with 8k shared allows to set 0038 0039)

I was thinking: the 2Mhz clock would not make the latch for the Z80 'bus' faster and as long as an instruction aligns well (multiple of 4) this might be OK.
However, the ld bc,0d030 takes 10 cycles so moves to the 'next', 'stretched', 1Mhz IO slot.
Z80 IO is (according to C128 manual) also subject to clock stretching by VIC.