First few weeks under the new rent cap rules and, honestly, nothing dramatic happened. Which might be the most useful data point of all, given how much noise there was leading up to it.
My own properties weren't affected, I don't raise rent more than annually anyway. Talked to a property manager who handles a much bigger portfolio, and her read was similar. The landlords who were increasing rent multiple times a year were a small minority, and they've simply adjusted to doing it once, at a larger amount, instead.
Whether that's actually better for tenants is a separate question I don't have a confident answer to. Frequency capped, but amount uncapped, means the same total increase can still land, just concentrated into one bigger jump instead of spread out. Worth watching how that plays out over the next twelve months.