They are not waterproof. You need to spray a clear on them and let dry. Then you wet so they can be transferred to the receiving surface. I have had mixed results doing this successfully, say one in three attempts.

Regarding the fading I have not noticed that.

The lack of water resistance is an interesting one. I have thankfully not encountered any moisture resistance issues with my inkjet decals. Fade can take years to notice. Results may vary with your particular combination of decal paper and ink. I shoot epson k3 archival inks from a high end printer simply because I have one. If I did not have that I would get my decals laser printed at a shop.

https://en.wikipedia.org/wiki/Inkjet_printing#Durability

Durability
Inkjet documents can have poor to excellent archival durability, depending on the quality of the inks and paper used. If low-quality paper is used, it can yellow and degrade due to residual acid in the untreated pulp; in the worst case, old prints can literally crumble into small particles when handled. High-quality inkjet prints on acid-free paper can last as long as typewritten or handwritten documents on the same paper.

Because the ink used in many low-cost consumer inkjets is water-soluble, care must be taken with inkjet-printed documents to avoid even the smallest drop of moisture, which can cause severe "blurring" or "running". In extreme cases, even sweaty fingertips during hot humid weather could cause low-quality inks to smear. Similarly, water-based highlighter markers can blur inkjet-printed documents and discolor the highlighter's tip. The lifetime of inkjet prints produced using aqueous inks is generally shorter (although UV-resistant inks are available) than those produced with solvent-based inkjets; however, so-called "archival inks" have been produced for use in aqueous-based machines which offer extended life.

In addition to smearing, gradual fading of many inks can be a problem over time. Print lifetime is highly dependent on the quality and formulation of the ink. The earliest inkjet printers, intended for home and small office applications, used dye-based inks. Even the best dye-based inks are not as durable as pigment-based inks, which are now available for many inkjet printers. Many inkjet printers now utilize pigment based inks which are highly water resistant: at least the black ink is often pigment-based. Resin or silicone protected photopaper is widely available at low cost, introducing complete water and mechanical rub resistance for dye and pigment inks. The photopaper itself must be designed for pigment or for dye inks, as pigment particles are too large to be able to penetrate through dye-only photopaper protection layer.

The highest-quality inkjet prints are often called "giclée" prints, to distinguish them from less-durable and lower-cost prints. However, the use of the term is no guarantee of quality, and the inks and paper used must be carefully investigated before an archivist can rely on their long-term durability.

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Most home inkjet printers are going to use water soluble ink that will run if it gets wet. So keep that in mind.

I use a brother laser printer to print shipping labels. I got it a couple years ago black friday special for like $50. Went through a couple toner carts (used generic brand, was fine except one bad one) and now the imaging drum has a score mark and is just going bad. New drum costs like 3x what I paid for the printer... which came with a drum.

Printers they give them away probably losing money on sales on the hopes you spend $$$ on the consumables which is where all the profit is.

Sunday at 2:35PM.

If you are doing black only, such as insert lettering and keylines, then laser is the way to go just because you don't have to worry about sealing the ink. Also in some cases, "black" inkjet ink is actually dark blue like a Sharpie.

If you are doing any sort of color, the calculus gets more involved. Most color laser printers do not approach the fidelity of inkjets when it comes to blending and dithering for a wide color gamut. Color laser = spot colors for charts, lines, graphs whereas inkjet allows photo dithering. That said, color lasers are way better than they used to be so for some uses including photos, you might not notice a significant difference. So it would depend on the application: not all playfield art is the same. You might be able to get a good color match from a laser; it would probably be far easier to get an exact match from an inkjet. This is noteworthy if you want to print an overlay or something.

When I did custom model railroad decals, I was able to print extremely complex graphics in exacting color matches with the high-quality inkjet I had at the time. Getting those same results from a color laser would have been impossible. So I had to seal the inkjet decals, but I had good results even though it was a slightly tricky process.

I have an obsolete ALPS printer which uses water-tight opaque film ribbons, but requires full layer separation for CMYK/RGB color so its color palette is fairly limited. Which is why I usually only do black and/or white with it. I would NOT recommend an Alps for a newbie though. They are wonderful and missed but not for the faint of heart these days.