

When you get the hang of driving stick, which you will pretty quickly, you can try matching revs on downshifts to smooth things out and then you can try heel toe with matching revs.
This I definitely do recommend once someone is comfortable with the basics, particularly the rev matching on downshifts. It both makes driving smoother and makes clutch wear once moving negligible so in the long run you save money too. I consider rev matching an early intermediate level skill - not something I’d trouble a raw beginner with due to information overload but something that should be learnt before they start thinking it’s too hard (because while it is not hard an unfortunate number of people will tell others it is).
Heel toe shifting can wait until people are comfortable with driving in general but I think is something one should learn if one enjoys driving - if only because it’s just plain satisfying to do. Again this is a technique made out to be difficult but it’s really not that hard (though how much foot manoeuvring is required does vary between vehicles).
When you get really good you can shift gears without engaging the clutch just by rev matching, but don’t try that til wayyyy later. Can mess up the gears.
This one however I recommend people keep in mind is possible (in case one ever loses clutch movement) but keep to a bare minimum on synchro boxes. Try it a couple of times to show yourself it works but you do have to be very familiar with the car to do this without putting wear on the synchros (keep in mind that if it didn’t slip in like butter you didn’t get it quite right and the synchros had to pick up the slack for you). It’s more easily done with a non-synchro box as these both give obvious auditory/tactile feedback when you’re doing it wrong and tend to have wider engagement points for the gear dogs to slip into. Motorbikes for example run non-synchronised gearboxes and are typically very easy to clutchless shift as long as you’re upshifting while accelerating and downshifting while decelerating.
I don’t think they were saying you shouldn’t ever look at the tacho, but that you should learn to be able to pick your shift points without having to look at the tacho.
As you say you do want to figure out what revs works best for a particular vehicle (having driven/ridden vehicles with redlines between 2500 and 19000rpm there I can say there is a little bit of variability to be found out there) but it shouldn’t take long to figure out what this sounds and feels like for regular use.