The reason for videos like that is CYA, employers have to document then "learned" us, to reduce their liability. Same goes for other topics, like what is allowed or not allowed when hitting on coworkers, and how to respond to delusional coworkers who deny nature and chromosomes.
Not counting static and ignition systems, 10kV or so is quite dangerous, can burn your whole arm in an instant. For those of us in the field, training videos and pictures show the aftermath. I've watched PG&E guy use a fiberglass pole with non-contact voltage detector before working on underground transformer.
Also, high power sources like utility transformers can cause a DMM or a circuit breaker to explode, and can make an arc far more intense than an arc welder, causing instant skin burns.
There are non-contact detectors available for low voltage (< 600V) use as well, such as one setting on this meter:
I have a basic acoustic stud-finder, but some have magnets to find nails and voltage detector to warn before you drill/drive into a live wire.
You can check for voltage with leads of a DMM, but then you're bringing the voltage out to an exposed other lead of DMM. Be very deliberate about not touching it! If you have an alligator clip for one lead, you can work with one hand (keeping the other behind your back) and attach clip to ground, then probe a wire to test it. But that doesn't take care of testing between wires. I hold both test leads in one hand while contacting two terminals.
Our training and policies emphasize "LOTO", Lock-Out Tag-Out. After determining which breaker operates a circuit, we turn it off and put a lock on the breaker/disconnect and verify with a meter there is no voltage between terminals or to ground. A tag identifies what, when, who.
For you, this means shutting off all sources of power to a box before working on it, and making sure family members can't turn it back on.
Some devices have multiple sources of power which must be disabled.
For PV systems, the difficulty is PV panels and batteries produce power that can't be shut off. So need to isolate them; after interrupting current flow I unplug both ends of MC connectors at PV panels.
Batteries, usually don't have touch-safe connectors to work with plus a wrench can short them out and melt, so insulated tools and being careful about order of connections is useful (e.g. in a car, disconnect ground cable first, reconnect last. That way, when working on positive cable, if wrench contacts car body it doesn't complete a circuit.)
If chassis (or doorknob) is electrically hot due to previous work, that's something you want to find out before touching it. Non-contact probe migh work. A meter could, but you have to have a second conductor to test, one that is actually grounded. Working on ungrounded kitchen & bath outlets, I used faucet confirming voltage present, then absent. Also identifying hot vs. neutral. An extension cord to an outlet could also serve as reference.
I got bit by hot chassis, which I did to myself. Wired hot vs. ground swapped and didn't consider the possibility while debugging low measurements. It is especially important to avoid a shock in one hand and out through the other. Best to have rubber shoes, do not lean against or otherwise contact ground, use one hand to make measurements.
And you're to blame, You give solar a bad name! Meant to be safer than a cheater cord, power cord with shrouded banana plugs + Similar wire and banana connected to equipment under test. Now it's easy to stack banana plugs and plug in HV scope probe. It's just as easy to mix up Line and...
diysolarforum.com
The key defense is awareness, thinking things through before touching anything, and testing with a meter.
