The kickr can cope with the transitions, but it’s a slightly different workout depending on mode.
In ERG you ideally spin up to around 100 rpm a few seconds before the orange sections and then ‘catch’ the power surge. Then you need to keep spinning for an extra second or so for the power to dip. I find sometimes this lags several seconds.
Alternatively you CAN wait for the gun but it’s a lot trickier and you will inevitably end up grinding through the start (or all) of some intervals.
In level you can work out your correct gear (and/or level) to be as close as possible to the target and spin up to it more ‘naturally’ each time but it relies on you to be honest with yourself to do the full 15 seconds even when it’s really burning and maintain consistent form to keep the power up.
Personally, I’m in two minds because I’m not sure what I’ll need left in the tank for Norway. I’m confident of grinding through GOAT in most scenarios, the focused plan says do HIE at 80% but my AC was poor last FF, wildcard option would be do it on RPE.