Low download speed with rtl8821ae - x86-64 installation

I'm creating an router for my brother with Asus VivoPC VC62B. It has dual-core Celeron 2957U, 4GB of DDR3. It has integrated Realtek 8169 NIC, which is going to the switch, and plugged in USB3 1Gbps NIC which is working as a WAN port. This configuration is working fine on the newest OpenWrt 23. Over the cable I'm having stable 200/40 which is what my ISP gives me - no problem here.
The problem is a M.2 WiFi card, which lspci says it is RTL8821AE. I have installed the kernel module and configured the WiFi. But whatever configuration I will try, I'm stuck on ~4Mbps download and ~30Mbps upload rates.

root@router:~# cat /etc/config/wireless 

config wifi-device 'radio0'
	option type 'mac80211'
	option path 'pci0000:00/0000:00:1c.3/0000:04:00.0'
	option channel '5'
	option band '2g'
	option country 'PL'
	option cell_density '0'
	option htmode 'HT20'

config wifi-iface 'default_radio0'
	option device 'radio0'
	option mode 'ap'
	option ssid 'Sierotka'
	option encryption 'sae-mixed'
	option key '******************'
	option network 'home'
	option ieee80211r '1'
	option mobility_domain '****'
	option ft_over_ds '0'
	option ft_psk_generate_local '1'
	option time_zone 'CET-1CEST,M3.5.0,M10.5.0/3'
	option bss_transition '1'


Just wanted to document my experience with recently attempting to use a rtl8821ae on x86. I have the exact same issue that my upload maxes out my speed, but my download is pinned at 4mb/s with this network adapter. I did find that option cell_density 3 does make it download at 24mb/s. Though that is of course less than ideal as it's not downloading at full speed (my wired gets 500down as expected).

RTL wifi cards should be avoided, get an old router or AP and run the wifi from it.