The performance shown on R2S vs RPI-3B is very interesting. I wonder who can try editing OpenWRT in this way and test it on R2S:
diff --git a/target/linux/rockchip/armv8/config-6.1 b/target/linux/rockchip/armv8/config-6.1
index 1830a89c93..687192583d 100644
--- a/target/linux/rockchip/armv8/config-6.1
+++ b/target/linux/rockchip/armv8/config-6.1
@@ -491,12 +491,7 @@ CONFIG_POWER_RESET=y
CONFIG_POWER_SUPPLY=y
CONFIG_POWER_SUPPLY_HWMON=y
CONFIG_PPS=y
-CONFIG_PREEMPT=y
-CONFIG_PREEMPTION=y
-CONFIG_PREEMPT_BUILD=y
-CONFIG_PREEMPT_COUNT=y
-# CONFIG_PREEMPT_NONE is not set
-CONFIG_PREEMPT_RCU=y
+CONFIG_PREEMPT_NONE_BUILD=y
CONFIG_PRINTK_TIME=y
# CONFIG_PRINT_QUOTA_WARNING is not set
CONFIG_PROC_PAGE_MONITOR=y
On Raspberry Pi 4B with CONFIG_PREEMPT_NONE we can reach 1.1Gbps. But if we keep CONFIG_PREEMPT, the speed will be reduced to around 670Mbps. You can see the thread here,