3DPrinting

Which workbench do you mean? Are you okay with basic sketch/extrude, part design works well enough, but as you say constraints can be a pain. Tbh just assume you're working with the points for the most part - polylines work fine for slightly more complicated shapes.

My "formal" CAD training was Dassault Systeme's CATIA V5 training manual, so I tend to default back to that. For basic geometries, use basic polygon shapes/combinations of those, for anything more complex I tend to use a polyline and sketch out a rough shape, then fully constrain to the dimension I need. If the geometry goes all to hell then stop and just use the mouse to grab a point and pull it back to where it should be before you go any further and then constrain it. (My sketches tend to be noisy with constraints just FYI).

Mangojelly's guides on YouTube will get you pretty far (though he doesn't constrain as much as I personally would, I suspect this is just because he's demoing techniques rather than giving best practice at all times. he knows the software/techniques super well and is great at explaining it).

Based on Mango's recent video there are a ton of enhancements for sketcher constraints on the latest dev branch, so hopefully they'll be on main soon too.

If it's assembly constraints, the only assembly workbench I've used is assembly3 - it works kind of how you'd expect an assembly workbench to work, but you do need to hold its hand a bit. I've gotten into the habit of, import as step, rename part, add to list of parts, use linear translation with the mouse to get the part roughly where it needs to be and then start applying constraints to put it where I want it.