Flexible vents should not be used. 35' max length. Subtract 5' for every 90 degree.
https://www.nachi.org/dryer-vent-safety.htm#:~:text=The%20maximum%20developed%20length%20of,degree%20(1.6%20rad)%20bend.
If you tee into 1 vent, use a backdraft blocker. [1]
Rigid duct is required within wall cavities. [2]
