Autoflower topping?... and if so, when is best?

From my very limited experience, what I plan to do in the future is grow Auto's without topping to start with, see how that strain grows then the next time I grow that strain I will have a better idea how it will grow and then decide to top or not. The Afghani #1 Auto I'm growing was so vigorous growing that I could have easily Topped it, though LST has worked really well on it and its covered in buds.

I only grow autoflowers and personally would NEVER top them... you just don't know precisely what their schedule is going to be... I've had some that go into pre-flower in Week 3 and some that don't go into pre-flower until Week 5... if you top at Week 3 and they're wanting to go into pre-flower, well, you've screwed up their timing and they won't recover... The most I've ever done - and WILL ever do - is a lot of LST to get the bud sites that are naturally there to be the biggest they can be. Leave the topping/fimming etc for the photoperiods... My opinion. Good luck!

To be honest I haven't topped mines this time but usually I do it. There can be occasions where you can extended the veg state even if it's an auto, one time I had an auto white widow stuck in veg state for about 3 months and over. It's a mix of light cycle changes, nutrients feeds and cutting off any sign of pre flowering growth. This will probably have an effect on the yeld at some point as I am not sure the auto would benefit from this treatment, but I like to experiment when I have more than one plant available. Best thing would be to top her if you have another one growing on the side so you can compare the differences and learn which strain can be more subject to stress.. The technical details of a strain might help as well, go for the high tolerance to stress and the ones that grow in height a lot, those will be able to handle topping much better.

I like hundreds and thousands and chocolate sauce

As a rule of thumb, one should stress a plant that is healthy, vigorous and large enough. Otherwise techniques are counterproductive. I would leave it alone for now and concentrate on getting her growing, maybe some LST in a couple of week if you manage to get her going.