Ap has more burst but doesn't have sustain like Ad. If you play right Ap can work in high elo like blotter, Ap Teemo is good because it takes out Ad carrys quickly and with my build you still have splitpushing potential with Runaan's. Ad is still fine and with gunblade you do still have some burts but in my opinion Ap is better just have good placement so you aren't 1 shot.

Use Q as much as possible in lane and if you can go for a flash Q under their tower but make sure it will kill them. A control ward must be placed in river bush and mushrooms places in tri bush and river and then you're ungankable unless your tower is low then they can come from behind.

If you are bad in lane then stay under your tower and farm up. If you can't get a kill in lane then go into their jungle when you know they aren't there and try and get a kill on their jung (unless they are fed or tanky etc), I usually hide by top side buffs wait until it damages them abit and then Q get thunderlords of and then they should be dead sometimes put a shroom infront of the buff they don't expect you to be there but don't do this alot for the love of god they'll just expect it.

Using Teemo's passive (Guerrilla Warfae) is really good as when you leave invis you get more attack speed (level 1-20% level 5-40% level 10-60% level 15-80%) but only for a few seconds. This passive is good when you camp their jungs buff but remember to auto Q auto.

TP and flash if you don't take TP then you are either really good and know you will win in lane or just stupid, its always good to have TP and you can go bot lane and turn fights around there's so many places where TP can be used and remember you can TP on your shrooms.