AP mode capable 802.11ax mini-PCIe (or rather M.2) cards don't exist yet.
Yes, there is the Intel AX200, which is useless for AP mode.
Yes, there are apparently the first samples for QCA QCN9074 available for sale from compex (no pricing yet, draw your own conclusions from that… around 200 USD for the 2.4 GHz model, around 200 USD for the 5 GHz model and around 250 USD for the 6 GHz model), but afaik those don't have driver support in ath11k (so far ath11k only covers QCN5024/ QCN5054 running on an ipq807x SOC) yet - and they wouldn't fit into your apu4b4 anyways (oversized, probably also drawing more power than the apu4b4 can provide; 802.11ax cards are running hot and need power). That said, it's questionable if the apu4b4 is fast enough to keep up with 802.11ax to begin with (at least the ethernet side isn't (and I'd be very sceptical what happens if you demand performance from both ethernet and wlan via PCIe concurrently), yes, 802.11ax can be faster than 1 GBit/s ethernet in practice, not just in theory) - and it only has a single mini-PCIe slot available (the other two are only USB XOR SATA and USB-only, but don't offer any PCIe lanes), while you'd need two (and both allowing oversized cards).