How will it grow?

Topping can be beneficial, as long as you are not growing auto flowers. Defoliating small seedlings is not a great idea............less leaves = less energy being made = less potential growth................but it is too late now, you can't stick them back on. LST is always a good idea. There is no such thing as "root stress" that is caused by training and there is no need to "counter support" anything,..... your plant will be just fine. In future, if you are unsure, ask questions before you do anything, not do radical things then ask if it is ok, you can't un-do what is already done! Also, if you think you may have more questions that you would like answred in the future, start a diary. The more info about what you may or may not be doing, the more accurate the answers can be.

It should be fine as long as you let the plant rest now without any further topping for at least a week or two. To minimize root stress, I'd recommend adding counter support at the stem base, like this: https://cdn.shopify.com/s/files/1/0528/5507/9112/files/ezgif.com-gif-maker_1_595298ab-dab4-4988-a5ad-2cdd66eb240a_600x600.gif?v=1626284254