Tubeless is fantastic, but there are a few iffs and butts.
Your tyre has to be just right. If you want official "rightness" go for a UST and place that on a UST certified rim. UST - Universal System for Tubeless (or whatever the real French wording is), is Mavic and Hutchins invention and specification that's available to others in the industry provided they play nice and stick to the spec. The standard or spec, calls for a tyre and rim system that will seal without the use of a tube, or tape, or rim strips or sealant. This does not mean that it will not deflate when punctured. That's what the sealant is for. But for UST the sealant is not required to keep the tyre inflated on the rim, sans tube.
Now, many variations of tubeless, other than UST exist. For instance, you can use a UST tyre on a standard rim and just tape up the rim. You could use a non-UST tyre in the mix or, you could use one of the non-UST tubeless tyres/systems which are generally called tubeless ready. The Tubeless Ready guys are the ones that don't want to pay a license to the French to put UST on their tyres or, who won't get UST approval because of one or other issue.
It is a bit of a minefield.
Many tyres work but they must have thick sidewalls that aren't porous. If you can see the cords through the sidewall, chances are good that the tyre will not seal, even with sealant. Some sealant is better at sealing up thin porous sidewalls than others but for a beginner, with so many variables in the mix, this is a no-no. Choose a tyre with a thick, juicy bead, not a thin hard bead. The juicy bead seals better on metal than a hard bead with a thin layer of rubber over it.
When it comes to sealing the spoke holes, you have many options but also issues. You obviously need a tubeless valve, which works a bit like a car valve. Getting these to seal on rims not really designed for them is a book's worth of writing, but generally, you want to make sure that as much rubber on the valve contacts the metal as possible. Sometimes you have to enlarge the rim's inner hole to get more rubber in there. Generally these valves have a conical rubber foot that needs to wedge tightly and seal. Some companies have "systems" of matched rim and valve foot profiles. These are the best, but obviously of no use to our vanilla brand rims.
As for the spoke bed sealing, you have to issues to consider. a) The tape or strip has to resist the force of the air pressure inside the tyre and not stretch and pop through. b) the strip must sit tightly and not come off when the tight, juicy bead slides over it during installation. Here, the Stan's yellow tape is somewhat good, but far from perfect. The problem is that the tape has to be hard and pliable. It must be pliable so that it follows the rim's inner contours but it must resist popping into the holes. It must also resist the sealant sloshing around over it from lifting the ends and causing sealant creep underneath. This is a disaster if it happens. Long story by itself. I have had success with self-vulcanizing silicone tape. The term vulcanizing is a bit misleading because only rubber can vulcanize, But you get my point.
Then, you have to decide on the appropriate sealant. This stuff - horrible, all of it, comes in two broad varieties. Latex-based and glycol based. The former is preserved with ammonia and corrosive to naked aluminium. It seals well, has a short life in the heat (not a problem in the UK) and is incompatible with CO2 inflation. Glycol sealants work best on thick UST type tyres because its sealing mechanism is not a glue that cures but a carrier with rubber crumbs inside that blocks the hole.
Getting the tubeless to seat the first time is quite a story and you need six hands, a compressor and a bucket of soapy water.
The 20" tube method you mention is called the Ghetto method. It seals very well but you have to fit a new tube each time you take the tyre off.
In operation, tubeless is wonderful. It is not perfect though and can burp when cornering or bumping through. In the field, if you have a total deflation, you have to fit a tube. This is messy and tricky because your tyre now looks like an invented hedgehog inside from all the thorns in there. You have to remove them all before fitting the tube.