Hi Darren,
Yes I am familiar with and have used the first 3 of these. The fourth is too buried to be useful and offers no particular advantage over option 3 both uses a custom Google Search. All have their deficiencies. Let me explain:
1. The Category picker on profiles, like most picklists is excellent for adding categories to profiles once you are familiar with the range of profiles and how each is intended to be used. However, it does not use Boolean Logic, so it takes time to realise that WWI only finds a handful of options, whereas World War One finds many more. It also does not follow the convention used everywhere else in Genealogy or indeed the rest of Wikitree - to use the historical naming convention or even to allow it to be used as a look up reference. Granted there is a case in the case of World War One over WWI, given Google returns 3.85 Billion results for World War One, while only 156 Million for WWI. World War 1 however runs a close second with 3.77 Billion, so that is 3.77 billion article writers who would be slow to find a category of World War One in a picklist and 156 Million who would be lost. It must be noted that good webdesign dictates that pick
2. Find Categories is next to useless, as it again assumes knowledge. You have to know in advance how information is organised and it does not allow you to use the more commonplace web navigational method of using multiple paths to get to a target. As such you can find yourself clicking through multiple pages to find what you want. Per the example in the original question, Australian Army Generals ideally should be found via a navigational construct of Australia>Army>Generals AND Military>Generals>Army>Australian AND what ever other relevant association that people might commonly use based on their own cultural constructs.
Further, it took 5 clicks from the profile I may have been working on to find Australia, Army Generals, which may or may not be what I'm looking for since I am actually looking for Australian Army Generals, which means I might ignore it and keep looking just in case. IF I click though, I find information that provides a definition that confirms this is the right category, BUT, nowhere on the page does it tell me how to add it to my profile. From there I either have to go back to method 1, now I know what the category is at least called or else I do what I did for my first 6 months on Wikitree - I open one of the profiles linked to category page and then copy the category wiki markup to my own page.
Good web design says you should never need more than 3 clicks to find what you are after. It should provide multiple paths to and away from the page and breadcrumbs to find your way back. It should provide text and visual clues as to where you are and where you need to go. It needs to be accessible and inclusive to people of all cultural, educational and physical ability. Can you honestly say that Find Categories delivers anything close to good and accessible design that supports our promoted brand value of collaboration?
3. and 4 are two different ways to a Custom Google Search, which while it follows a convention that billions of people understand, it also fills your first screen of text with promoted sites that have nothing to do with Wikitree. For someone not internet savvy (think Accessible again), they may click away without scrolling down. Needing to scroll to find what you want initially is another web design no-no of course!. The other problem with Custom Google Searches are they are not time bound unless you configure them that way. This means that it does find "Australian Army Generals" - Hooray! - even though the category has now been changed, Google remembers what is was before. which can be good and bad.
While Robotic Process Automation Technology (ie. Editbot) seems efficient, without real culturally and historically sensitive collaboration, it can also alienate the very volunteers who spend hundreds of hours of their own free time collaborating and researching to create the 20 Million profiles and counting on wikitree. Without those willing volunteers, Wikitree is nothing.