Improve local transfer speeds with AC86U

I just installed a new RT-AC2900 with the latest stable Merlin 384.13.
The iMac is connected via gigabit ethernet and the iPhone 11 Pro by 5GHz with reported TX/RX Rates 866,7.

I tested transferring some files from Mac to phone, and I get on average 28 MB/s (224Mbps).
Are there settings to tweak to go faster or is this it?