Enable soft offload, if you need roaming between 2 radios check here:
My result RT-AX54 (same baseboard, just one more LAN port) against 1000/500 FTTH without offload with all 5 mods:
https://www.waveform.com/tools/bufferbloat?test-id=6d1dfbe0-c7af-4954-bed6-eabf24050c44