Krown washes off quickly, and application thoroughness is spotty at best, at least in my experience. Rust Check (common in Canada) washes off easily as well, although yearly application of their thicker product "Coat and Protect" holds up better. I gave up on having someone else apply anything as time and time again they missed large areas. Basically anything they can't see underneath does not get touched. Cavity spraying tools etc. are relatively cheap to purchase for DIY application. All of the products are pretty messy, but Noxudol 300/700 is my favourite as it doesn't drip a lot.
I don't use Fluid Film or Woolwax (lanolin based products) as they are not kind to rubber long term. Otherwise, with yearly application, they do work. They are pretty idiot proof to apply for prep, but you do need to avoid rubber trim, harness connections, bushings. I use FF on my snowblower because it's cheap for summer storage. PB Blaster Surface shield is a blend of lanolin (and apparently petroleum jelly) which gives it better wash off resistance.
I'm using Noxudol 300/700 on our vehicles. It firms up to a wax consistency 4-5 days after application, has zero solvents, and integrates chemicals which react with rust. On a new vehicle these two products are excellent. 700 goes inside panels for high creep, 300 on the chassis for better wear. On existing rust, adhesion with 300 can be an issue if your prep is not spot on. They are fine for electrical connections, rubber etc. which makes them a better choice IMHO, particularly for EVs. I use about 1 litre on average per year for touch ups with the Noxudol 300 on high wash areas on the car bodies behind the front wheels and immediately front/behind the rear wheels.
I've not used Waxoyl Hard Wax Plus (for exposed chassis) but I would like to try it as they has a similar additive package as Noxudol (based on MSDS) but adds 1-3% phosphoric acid which bodes well for reacting with existing rust. It's expensive though, at $290 CAD or so for 5 litres. The non-aerosol product MSDS is here:
https://www.waxoyl-usa.com/assets/pdf/Hardwax_Plus.pdf Note that the aerosol product omits the phosphoric acid but still has sulphonic acids and calcium salts. You want these for reaction with existing rust...
I can find zero evidence of Krown, Rust Check, FF, Corrosion Free etc. containing anything that actually reacts with or actively slow rust....they are just water displacers. I think the franchises like them because they don't need much for prep. Been testing all this stuff here in the salt belt for the last 35 years or so. Noxudol has been spec'd by Toyota and a few other OEMS in their frame replace/repair compaigns.