It should be possible to change the default client config - specifically, the itemTraderRenderLimit so that it defaults to 1 for all players on a multiplayer world.

First off, I didn't make the config system, Forge did, so I don't really have any control overs its feature list.
Second off, if you want the "default config" value to be set for everyone on a server, simply include the config file in the modpack when you share it with your friends and/or players, cause I know both Curseforge and Modrinth support this...