I usually start LST as soon as I have enough plant to start actually tying things down. I wouldn't top an auto. The less stress you can cause to the plant the better it will grow and the higher your yields will be. Just make sure you take it slow and easy so you don't wind up breaking any branches. The LST I see in the latest pics you uploaded looks good. Let it grow more and that top branch will start growing upwards again. Once that starts happening just move the tie further up the stem to keep it bent down.