You can tie a plant pretty much any time throughout the grow without issues as long as you are gentle to not break the plant stems. I think everyone here who ties their plants do it at different times depending on their grows. I know some peeps will let a plant get about 8" tall and then bend the whole plant over before the stem gets woody enough to prevent bending. This will allow many nodes(6-8) to form and then all of those nodes will sprout branches that will shoot out and up to become multi-cola tops.
Some peeps will let the plant get to about the 4th node and then top it to create a twin top, then when the twin top and the branches below that begin to grow out to be 4-6" long, they will tie all of those branches and bend them out horizontal in order to cause the plant to open up and spread out. This is all done in veg so that the plant will get wide before turning up toward the light.
If you are going to do a scrog then you don't need to tie them at all. For scrog you would put 1-4 plants in a space(I wouldn't do scrog in a 4'x4' space as that would make it very difficult to reach and tend the plants in the back, unless you have access to front and back of the 4x4) If I was going to do scrog in a 2'x4' space, I would put 2-3 plants in and let them get 4-6nodes high then top or fim to cause all the lower branches to take off growing.
Then I would set my screen over the whole thing at about 10"-12" above the top of the planters. As the plants grow up into the screen, you push the branches back under the screen and cause them to grow out horizontally under the screen. This will take several weeks to fill up the screen with branches as you will continue to push any branches back under the screen as they try to grow up through it. Once your screen is 90% full of branches you can flip the lights and allow all the smaller branches to grow up through the screen to become the buds.
This is a pretty cool way to do it but it is also pretty maintenance intense to care for them to that it does right and not just grow up through the screen as a normal grow.
I am glad to explain anything you need to know if you want to ask me specifically(PM) or you can ask the forum and get a concensus from everyone.