Based on your plans, I would say get a 20" bike because of the gearing options.
I have a 16" Mantis with a 60t/12t combo and it tops out pretty slow.
It would only be fast if I had a 65/70t chainring which gets expensive.
A 20" bike with a 55/60t chainring can get up to speeds where wind resistance will be your limit.
Also the smaller tired Dahons have shorter wheelbases so you don't want to ride fast.
With the distances you plan to ride, get a 20" tire bike.
The Jifo will take longer to ride the same distance and I doubt you could ever get a 65/70t chainring on it.