you only need a screen if the hole at the bottom of the bowl is big, my friend has a bowl and we never used screens when smoking out of it, as for my piece i have to use a screen cuz the hole is big, as for the carb just lift your finger off quickly and return to hitting the cherry until done
A 4-5 inch glass pipe with a carb is the best. Smoke, then stick it in your pocket and you're in stealth mode. They fit in your hand really nice, deliver a smooth and strong hit, and don't get too hot after a session. With bubblers, there's water to worry about, and with sherlocks and other weird shaped pipes you can't walk around with them in your pocket very well.