I was previously spoiled by strangely good-natured lines but I recently came around to the fact that the modem firmware matters. A lot. If you use the VRX202 modem chipset, and most modems/modem routers do*, the difference is the firmware it runs. And with OpenWrt you are free to try out different versions and find the one that works best for you.
*) certainly all the OpenWrt supported VDSL modem routers -- but the Vigor 165 runs a VRX518 modem chipset, that's another beast entirely.
P.S.: I'm currently reliably synching 101/43 out of 111/49 on a 100/40 vectoring line and actually getting full line speed using my Fritz!Box 3370 running OpenWrt (19.07.1, software flow offload enabled, but no SQM since I really don't need it). So I'm not entirely on board with blanket statements that the Lantiq routers are a bottleneck. They are just about able to manage a 100 mbit downstream.
