Robert, sorry. In my personal experience there is no clear answer to some questions. No formula that fits all. Others may have different opinions.
What is the right angle? "Sharp." A burr? Maybe, maybe not. Carbide? Maybe, probably not.
I should say that I don't use normal scrapers for shear scraping. I prefer gouges instead so some of the following, such as the burr and angles, may not apply.
The precise angle doesn't seem to matter as much as the edge being sharp. For example, I have shear-scraped with extremely small angles on the wings of a gouge and also on less extremely small angles, both with good results. I say "sharp" because that, to me, is more important than the angle. I like to shear scrape the outside of a bowl with a the wings of a spindle gouge. I sharpen with a 1200 grit CBN wheel on a Tormek (I used to use the Tormek stone water wheel). After I sharpen it I hone, strop, or polish the grinding burr away. When ready, the gouge is sharp enough to shave with (I sometimes test it on the hair my arm, just like a knife or skew chisel). Some people leave the grinder burr on a gouge and that works too, however, I believe a grinder burr is fragile and is knocked off fairly quickly against the wood. For me, a honed edge works better and longer.
The other John Jordan uses and sells a shear scraper that looks kind of like a wide skew chisel with a bevel on one side only. This is used extremely sharp and with no burr - the grinding burr is probably best removed with a fine ceramic hone. This works very well on the outside of his hollow forms and works well for bowls and things as well.
I think the more important thing than the angle of the grind is the way the tool is presented, with a gouge for example, how it is rotated along the axis of the shaft and how it is angled relative to, say, the top of the tool rest. What I do is start with a razor sharp tool the apply it to the wood and see what it does. If it doesn't make whisper thin, almost transparent shavings, I try a different presentation, different speed, different pressure, different tool. I find that some things work better for some woods and circumstances. It may seem like voodoo magic but that's the way I work. A simple formula is a good starting place but doesn't always do the best job (for me).
The tool needs to be sharp. In my experience that leaves out most carbide cutters, especially inexpensive industrial cutters with flat upper faces. They are just not sharp enough (to suit me) and when they get dull they are difficult to sharpen. With end grain they can tear out grain far more than a sharp steel edge. And any tearout can be difficult to remove by sanding. I once bought a set of the Easy Wood tools and was so horrified by the surfaces I got compared to a gouge that I sold them. I have no experience using them as as shear scrapers. If they remove whisper-thin shavings and leave the surface smooth and with no tearout then use them.
On a good day with good wood a nicely shear scraped surface needs very little sanding - I do little power sanding, often sanding mostly by hand starting with 220 or 320 paper, even finer grit for small turnings in hard wood.
For a convex surface (e.g., the outside of a bowl), a shear scraping edge is probably best with a fairly straight edge - this smooths out small imperfections in the wood. For a concave surface (e.g. the inside of a bowl) a shear scraper is best with a shallow curve, a little more curved than the wood. For the inside I usually use the rounded or tear drop shaped flat HSS scrapers such as what Sorby sells. When very sharp and held at a shearing angle, they can take off the whisper shavings that give a smooth surface. With these I do occasionally use a burr on the steel cutter, depending on how well it is working. When I use a burr it is usually pretty small and raised with a carbide burnisher, not from the grinder.
If this seems confusing with options, that's because it is. If new to shear scraping I would recommend starting with this: sharpen a bowl or large spindle gouge with long swept-back wings, hold the tool against the tool rest with the tool held at about a 45 degree angle to the right (or left, depending on the curve of the piece), rotate the tool until the lower swept back wing can be touched lightly to the wood (the flute will be "up" and/or rotated a bit towards the wood, perhaps even with the upper wing almost touching the wood for a deep-fluted bowl gouge). Touch the lower edge very lightly to the spinning wood and slide the tool to the left (or right - in the direction the flute is facing) and adjust the angles, pressure, and speed of motion to get very fine, thin shavings. This can be demonstrated in 10 seconds but is hard to explain in words!
I suggest trying many variations and different tools and discover what works best for you, and more importantly, what kind of surface you are satisfied with.
When I'm shaping a bowl or form I often do what as some others I know do - while shaping the piece and long before I get to the final shape I make lots of "finish" cuts then cut them away and repeat. I might try different lathe speeds, different tools, different body motions. A bit of each of these "finish" cuts can be shear scraped to experiment and discover what works best for that wood and that shape. Since I've done lots of finish cuts when approaching the final shape, when I finally get to the Final finish cut my hand and arms and stance are well-practiced and I've decided the best tool and method of shear scraping for that piece. Note that I'll never win a turning speed contest.
Videos may be ok for learning some ways to go about this. Live demos are great. But there is nothing better than spending some time with an experienced turner. Turning clubs are perfect for meeting and arranging personal one-on-one time.
EDIT: I forgot something likely important which almost everyone forgets to mention when they say what works for them - I mostly turn dry wood, cherry, dogwood, walnut, maple, ebony, olive, cocobolo, etc. The way I shear scrape works well for me with dry wood so I use the same thing for green wood. Something else may work as well or better for someone else when turning wet wood. I also do a lot of spindle turning and don't find much use for shear scraping there.
JKJ