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Here’s a whole topic discussing 2:1 v 3:1. I’ve only done 2:1 in my 5 months using SYSTM. It works for me. The referenced topic has thoughts from more experienced users. Bottom line: both work.
On rest days, I think all plans have easy and hard days. But I think the higher volume plans may use more recovery rides and fewer rest days for easy days to keep the volume up.