I own R2S/R4S/R6S, all of them are pretty good one.
First I would clarify that, RPi4 has much better processor than R2S, so routing in full GbE performance is just a piece of cake on Pi4, usually people getting trouble because of selecting a bad USB3 NIC (like those ASIX based model, if you use Realtek one it's just the same as R2S), but yes nowadays the Pi4 is still very expensive, 1GB model (hard to buy, seems to be at least 2GB now) + case + USB NIC I would say the R4S definitely beat it. I only recommend people using it when they have extra Pi4 on hand, using Geekworm metal case should be good enough, completely passive cooling works well.
R2S by default doesn't have WiFi, so if you install USB WiFi (not recommended for serious usage) you need to do some manual config, I won't say it's nightmare, most of the time is how you find a proper driver to work with it, and it has only USB2 port which won't bring you very good experience (well, using 802.11n 2.4GHz one can make a travel router use case here).
Upstream support on RK3328 is good (thanks to Google) so Armbian should work well on it now, but I believe most people want to use it as router so OpenWrt should be default choice, and of course using the vanilla OpenWrt, not FriendlyElec version.
Probably due to USB NIC, my R2S won't get me a very solid gigabit experience, ~800Mbps NAT LAN to WAN throughput is OK. For the extra processing power I inserted an old USB 2.0 SanDisk Curzer Fit 8GB memory stick (I have a few of them abandoned for some years) then ran PiHole inside LXC!
P.S. They also have R2C, which is similar platform but using USB-C power + another unsupported NIC so don't buy it, however when I received my R2S and I found USB-C power on it, thought they might have shipped me wrong one but in fact they already changed the design to use USB-C power (which is nice).