I think the main R4S forum thread has a few good discussions on packet steering. NanoPi R4S-RK3399 is a great new OpenWrt device
Search/read through that for good info on packet steering, irq affinity, SQM etc.
Also, the OpenWrt docs wiki has some info. Search that area as well.
One such page that you may find interesting is: https://openwrt.org/docs/guide-user/advanced/load_balancing_-_tuning_smp_irq