Personnaly im using kmod-r8125-rss (remove 8169) and add luci-app-irqbalance.
find /sys/class/net/eth*/queues/[rt]x-[01]/[rx]ps_cpus -exec sh -c '[ -w {} ] && echo ff > {} 2>/dev/null' \;
add the above to 40-net-smp-affinity under the r6s.
Software offloading off if using SQM, if not you can leave it on.