Bathroom and Dryer Exhaust Ducts

I have been reading up on 'proper' bathroom exhaust ducting. Sounds like Insulated Flexible 4" Ducting is the way to go. In my situation, I plan on venting each bathroom fan out through the soffit. I don't want to put holes in the roof preferably. I can use non-vented soffit where I will be installing the exhaust fan ducting. I figured this would prevent moist air from going right back up into my attic. Any pointers, or products to use for venting in the soffit?

For my dryer, I am thinking about venting through the wall, down to the floor and running between two floor joists out the house. This would be an 8' run. It also means a 90 at the back of the dryer to go into the wall and point down, then another 90 to turn right after the vent leads down in between the floor joists. Would the two 90's be a no-no and cause any issues? Is it best to use the recessed dryer vent box that the dryer exhaust can dump into, or just run standard ducting that ties into the dryer exhaust?

 

You'll have to look for it, but there is a soffit vent made specifically for your application. For the dryer, I would recommend hard piping rather than flex.

 

Soffit venting is just a bad idea.
Go thought the roof, done right there's no way it's going to leak or have warm moist air sucked back into the attic.