I was considering some 8dBi or 12dBi antennas and at least dropped the latter for its length of 25 cm.
And then been reading Increasing WiFi Range and that got me thinking that with a omni directional antenna a good portion still gets wasted in areas that do not require coverage but rather may (further) spam on the neighbourhood (same way they intrude my cover area).
Yagi antenna seems overkill for residential deployment and probably cause too much loss in wide angle coverage.
Directional antennas by design seems a bit bulky for direct attachment to the router, like this one https://www.alfadistribution.com/alfa-network-apa-m25-2-4-5ghz-dual-band-indoor-antenna/ but I think I will give a try.