Carry both, in case of a second flat. You do not need alcohol to clean tube before applying a patch; use small piece of sandpaper to roughen up tube. Glueless patches are not as good as the old fashioned system of glue/patch.
Even several patches on top of each other will not affect ride quality/balance.
We do not use liners or put goop in the tubes.
Watch where you ride and avoid roadside debris.