For a long while last year, I had an iPhone and my fiancé had a Pixel. It did not matter whatsoever in regards to the relationship. We used Telegram (still do).
If phone choice dictates someone's choice in partner it is probably safe to categorize them as "terminally online." Stay away from those people.
There is no double nat. Passthrough mode has worked as expected for me. The one issue I have is that the RG will maintain firewall states, so it limits you to the RG hardware for those states. I have a pretty large home network though, tons of devices, IoT, etc, and it has been stable.
Latency seems decent. I have an AT&T fiber 2gb symmetrical connection and a ping to google from my Netgate pfSense machine is around 10-15ms.
I used Plex for years, and it is the superior product (if you pay) compared to Open Source alternatives. However, after seeing Plex's recent incentive pivots and looking for investors I jumped shipped to Jellyfin. The thermometor of enshittification is indicating that Plex is on its way out.
Folks who haven't looked at alternatives yet, do so now.
I have the same Residental Gateway. Using pfSense+ on my end. The BGW320-500 is fiber capable. I assume you're using fiber? If so you cannot hook it into ONT because the RG is the ONT. In my case I get raw fiber into a PON module that hooks into the RG. Best you can do in this case is set the RG to "passthrough mode" via web UI (192.168.1.254).
I almost threw my hat in this ring but I must wait on people who use Linux to get ahold of it and review it. Proably an early 2024 buy date for me.