Was attempting to do a similar job myself, get a openwrtx86 build with 2.5Gbps bit more future proofing (as much can).
I skipped the Raspberry stuff due to security concerns mentioned on this thread here
The Celeron J4125, it is perhaps doable but there are some reviews suggesting its lacking that bit of extra power to really do 1gig+ both ways properly, see this review here. It should be noted its perhaps overkill so you may still be fine with the J4125.
These intel i225 and 6 chipsets are not 100% from sounds of things, connection drop outs and other issues so those Ali express boxes are hit and miss. Also tons of hardware issues, but again hit and miss.
I think you sadly need to look at the The other N5105 and N6005 hardware, but sadly you may hit 20-30 under load watts with that and maybe 15-20 watts idle but at least it should do the job and be more future proof.
I will post below some extra bits I hard read to provideperhaps other ways to reduce power comsumption.