Biggest problems I have faced for home networks : ISPs are poorly configured and do very shady things sometimes like DNS hijacking. More often than not poor ONU firmware or hardware means you will see weird things like latency spikes or straight up packet drops. Sometimes IPv6 won't work if the ONU is in bridge mode etc. etc.
This post is overkill but what mostly works for home networks:
SQM - like cake sqm in openwrt - will work wonders if don't have a great ISP. I have seen as much as 5% packet loss on one ISP who said thats acceptable for a home network. Just reduce the load until a point where packet loss is really low. Then use a DNS resolver. DNS resolver will be much more reliable like unbound for your local network as packet loss has cause really problems with DNS for me. Cheap home network equipment dns is not reliable. You could really just buy a cheap Pi and run a local resolver. It would work a lot better than your home router. You may also want to consider replacing the ONU. This is rather easier than you think. The ISP ONU are really bad. A cheap NOKIA SFP GPON is like 20$ on eBay and if you can figure out the PLOAM password and Serial and Mac and VPN ID of your ISP, you will be able to simply swap it for a more stable link.
All in all I would suggest for a simple home setup: get a cheap SFP GPON and replace your ONU. Get a cheap router (either router on stick with Rpi4 for <500mbit or x86 box with SFP for hitting 1gbps with the SFP GPON) and run your own unbound resolver. Get some APs and either wire them or get a cheap mesh router 3 pack on amazon (you can get a wifi 6 3 pack for under 150$ these days on sale) and run it in AP mode.