The internal penetration averages 1/16”. The preparation of the land is critical. To thin will burn through, and too thick will not allow penetration. Any offset is distributed around the joint. A good starting point when developing your own “feel” would be a 1/16” space and land. Some welders will set the amperage for a drag technique using a flat plate, inclining the rod 50* or so in the direction of travel, and adjusting the amperage high enough so the arc does not go out when the rod is dragged along the surface. Most welders have a remote by their side so they can adjust the amps as needed during welding. There is no oscillation on the root pass. Travel speed will vary around the joint. Try watching the back of the weld pool and watch it flow up and tie in both bevels.
The hot pass is either weaved or whipped. The cap is also weaved, many use 3/16” rod. Another capping technique is the “J” method (it’s a type of whip). It a quick forward movement down on one bevel (about ½”) then depositing weld back toward the weld. The same technique is performed on the opposite bevel which looks like a “reverse J”. These caps are very flat and uniform. As you mentioned 6G capping is more difficult since the amount of gravity is not the same on the bevels. This is where practicing really comes in. Most welders recommend working the weld puddle from the high side of the bevel to the low side. All craftsmen are proud of their finished product and welders are no exception. Appearance will improve with time. It will help if you can watch someone and have them watch you and give pointers.
The little surprises I mentioned (which are by no means the norm, but they will happen from time to time) are in the form of: holes, bad tie-ins at tacks, holes, drop through areas, more holes and ropy stringers. The interesting nicknames I've heard are colloquial expressions, sometimes a little rude and crude and usually used around the boys.