Welcome to the forum!
If you want to use Inkscape, I'd say your best bet would be to forget about following tutorials for other software. There are loads of Inkscape tutorials on youtube, and writtens ones elsewhere, as well. I maintain a list of those which I think are the best, on the Home tab of this website. There are some more on the IC Tutorials tab.
If you are a complete novice, I would suggest starting with Help menu > Tutorials > Basic, Shapes, and Advanced (don't worry about the one named advanced - it's not really advanced, and I don't know why in the world they named it that
) And from there, move to the Beginners section of the list I mentioned on the Home tab.
However, it sounds like you might be a bit beyond the novice stage, and ready to dive into youtube (if you prefer videos).
To answer your specific questions. We often find with Inkscape, that there might be a few different ways to accomplish a particular goal. Hhmm, well actually, I'm not sure what you mean by "sharp tapers for bezier curves".
If you mean you want a corner rather than a curve, then using the Node tool, you need to change the node type from Smooth to Cusp/Corner. Click on the node to select it, then change the node type using either buttons on the control bar or key shortcuts (Help menu > Key and Mouse Reference). Once the node is selected, you will see the node handles. You can adjust those as well, by dragging them. That's how you can adjust either corners or curves.
However, there's a way to draw heavy wide paths which are pointed on the ends, automatically, without needing to adjust nodes. For that you would want to use either Pencil tool or Pen/Bezier tool, and then on the control bar, choose the Shape option "Triangle In or Triangle Out". Or you can get both ends tapered by using the Ellipse shape.
I should warn you that Inkscape is not nearly as advanced as AI is, for that type of thing. As far as I understand, they have code that is similar to artificial intelligence code behind this kind of feature, with many, many different shapes or profiles available. So this is a specific example where you would not want to try to follow a tutorial for AI, and apply it to Inkscape. You'll get really lost. In Inkscape, except for what you see in the Shapes dropdown menu, you would have to create your own profiles.
For gradients "in the middle", I guess you're talking about radial gradients. Here's the basic steps that I use (other people may have a different approach).
-- draw the object which is to contain the gradient
-- Object menu > Fill and Stroke > Fill tab
-- click the Radial Gradient button (
)
-- switch to the Gradient tool (
)
-- configure the gradient by selecting the stops and changing color and/or opacity, add more stops, adjust the stops, etc.
Technically, you could also create a gradient which fits the description "in the middle" using a linear gradient, and adjusting the gradient so that it's symmetrical.
Inkscape also has a mesh gradient tool. It's very new, and I don't know of any tutorials for it. But it's not hard to figure out, and you can always ask us, if you need help.
I looked up "doll box art" and got a fairly wide ranging results. My best guess is that you want to achieve something like a shadow box effect? So that means simulating 3d with 2d software. Of course it can be done, but takes some skill, if you are after a realistic look. Typically that means using a lot of filters, and mainly simple gaussian blurs. The Blur slider at the bottom of the Fill and Stroke dialog allows you to add the simple blurs conveniently, without getting into the Filters menu or Filters Editor.
I'm not sure if I've ever seen any tutorials for drawing in a realistic style. I tend to favor that, in my own work, and I enjoy writing tutorials. So I might be able to make up a tutorial which shows just some very basic or general concepts or techniques. Or I could share an SVG file for a realistic drawing, and you could just dive into that, to see how I did it. Is either of those more preferable to you?