Both APs in the same place on their face (top room aiming downward) and only one powered at a time during tests. Used CH36. Export below. These settings gave best results:
add authentication-types=wpa2-psk eap-methods="" management-protection=allowed \
mode=dynamic-keys name=MySecurity supplicant-identity="" \
wpa-pre-shared-key=********* wpa2-pre-shared-key=*********
/interface wireless
set [ find default-name=wlan2 ] adaptive-noise-immunity=none allow-sharedkey=no ampdu-priorities=0 \
amsdu-limit=8192 amsdu-threshold=8192 antenna-gain=2 area="" arp=enabled band=5ghz-a/n/ac \
basic-rates-a/g="" bridge-mode=enabled channel-width=20/40/80mhz-Ceee comment=5G compression=no \
country=no_country_set default-ap-tx-limit=0 default-authentication=yes \
default-client-tx-limit=0 default-forwarding=yes dfs-mode=none disable-running-check=no \
disabled=no disconnect-timeout=3s distance=indoors frame-lifetime=0 frequency=5180 \
frequency-mode=manual-txpower frequency-offset=0 guard-interval=any hide-ssid=no ht-basic-mcs=\
mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7 ht-supported-mcs="mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,\
mcs-5,mcs-6,mcs-7,mcs-8,mcs-9,mcs-10,mcs-11,mcs-12,mcs-13,mcs-14,mcs-15,mcs-16,mcs-17,mcs-18,mcs\
-19,mcs-20,mcs-21,mcs-22,mcs-23" hw-fragmentation-threshold=disabled hw-protection-mode=none \
hw-protection-threshold=0 hw-retries=7 interworking-profile=disabled keepalive-frames=enabled \
l2mtu=1600 mac-address=E4:8D:8C:6B:94:1F max-station-count=2007 mode=ap-bridge mtu=1500 \
multicast-buffering=enabled multicast-helper=default name=wlan5G nv2-cell-radius=30 \
nv2-preshared-key="" nv2-qos=default nv2-queue-count=2 nv2-security=disabled \
on-fail-retry-time=100ms preamble-mode=both radio-name=E48D8C6B941F rate-selection=advanced \
rate-set=configured rx-chains=0,1,2 scan-list=default security-profile=MySecurity ssid=\
MyWiFi station-bridge-clone-mac=00:00:00:00:00:00 supported-rates-a/g=\
6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps tdma-period-size=2 tx-chains=0,1,2 \
tx-power-mode=default update-stats-interval=disabled vht-basic-mcs=none,none,none \
vht-supported-mcs=mcs0-7,mcs0-9,mcs0-9 vlan-id=1 vlan-mode=no-tag wds-cost-range=50-150 \
wds-default-bridge=none wds-default-cost=100 wds-ignore-ssid=no wds-mode=disabled \
wireless-protocol=802.11 wmm-support=enabled wps-mode=push-button
I tried to find the polar patten for the wAP but couldnt find anything definitive.