Way back, sun tour had a 3 pulley RD. That took up the extra Chain slack by having the chain path less direct,
but the wrap up was equivalent to a longer direct distance between, swing with just 2 pulleys.

SRam or S-A now offer hybrid cassette and Internal gear Hubs in a single Unit....

Way Way Back[57] I had a 3 speed with a triple cog cluster and a triple crank ,

I did have 3 shift levers to use on the 3 cubed 27 'speed' Sears-Puch J C Higgins..