“If the new toilets produce a lower flow per flush, then velocity drops below 2 fps in the main, and things pile up in the pipe until enough flow develops to flush things through...”
Toilets are a very minor portion of the water in a sewer...sinks, dishwashers, washing machines, etc....etc..
yes, unless they’re the only thing on the line, as the public toilets (location of the odor problem) are...