Very similar results to the AX-88U. The bottleneck is probably your iPad WiFi Adapter (negotiated speeds are probably 867 Mbps with two streams).
If you still have your AC5300 around an interesting experiment would be to try using it as a media bridge. I wonder if it will do any better than the AX88U Router + AC86U Media Bridge over 4 streams (
@Adamm managed ~ 1.3 Gbps with iperf
).
In theory the AX11000 router + AC5300 Media Bridge combo is capable of 2,167 + 2,167 Mbps. In practice I wonder if it can get anywhere near 2 Gbps (assuming 50% overhead).