I'm usually off the surface pretty quickly, but I start with a "temp" fort in the soil layer at z-2 for ~five years. Even unskilled miners cut through soil like butter, they can clear that first space and be hauling in on day 0 no problem (esp if its pitching goods down a hole next to the wagon into a QSP). My underground forts are usually increasingly elaborate mega-projects that take tons of time to dig out, smooth and engrave each layer, etc so I stay at this soil layer for 5-10 years or so before moving down into the fort proper. This setup also allows me to breach an aquifer at leisure (I embark with some starter stone on aquifer embarks). I spend a lot of time top-side constructing (and defending) since I rely on kill zones to space out invasion waves and keep my melee concentrated together with marksdwarf overwatch. I used to do that defense underground but lately I enjoy elaborate above-ground work. Probably due to the visualizers.
I'm not sure what you mean by a hunter dealing with an ambush, fleeing, I hope? I've lost really skilled huntsmen (ambusher/marksmen) to ambushers when I've forgotten to disable Hunting on migrants. It's been a long time since I've last seen a "real" goblin ambush but in my recollection hunters were excellent at uncovering ambushes, but surviving them is based entirely on how fast they could run and well they can dodge the Bowmen in that ambush. I feel that the Observer skill was greatly buffed at some point however and maybe my Hunter experience is based on days when their sight was a bit more myopic than is currently the case. In any case, migrants with Marksdwarf are valuable to me as military recruits so I'm risk-averse there.
I think I find that task speed just doesn't matter to me in most cases, I have my embark sequence down pat and after that the game tends to throw enough excessive manpower at me that executing tasks in parallel is efficient. The only time I really consider speed for miners is for Evil embarks to get under immediately. For instance, is brewing speed really that important? Even using completely unskilled dwarves I'm easily ahead of the booze game, its pots that are always the bottleneck there. Most of my 'waiting' honestly is aquifer and construction related.
Sorry if I'm dragging the topic too far down a side-road. The videos' are good advice so far, cheers!