I’ve only played vanilla Doom 3 online, and while it’s no suitable for competitive multiplayer, for casual fun DM and Coop, even stock Doom 3 played well with pings <150. In other words, if players are in the same country and on broadband, multiplayer feels fine (up to 4 players).
I’ve yet to try Doom 3 BFG online, people say it’s much better due to client-side entities and snapshots interpolation.
I haven’t played neither ETQW nor Brink online, so I can’t really say if SD improved networking of idTech 4 or if it’s beyond being fixed for optimal online experience