For what purpose? Something you can give to other people? Something where you can look for alternatives? The FIDE book cited by Alex lists quite a few tournament forms, but very few are actually alternatives to the Swiss and RR for individual tournaments—most are for team vs team events.
I hope you don’t need anyone to provide you with a brief description of a round robin. But what matters is not how a quad works (well, duh!) but how you divide people into quads, and since you don’t section quads according to the standard rules, it wouldn’t help to post a link to that even if you could find one.
For a Swiss, en.wikipedia.org/wiki/Swiss-system_tournament is probably about as good as any—it describes the general idea without getting into the really gory details that run for dozens of pages in the rule book.
Remember that was a tournament type is called may be a specification of one of the 3 basic types [Swiss, Round robin, & Knockout] of tournament. An example is the Quad tournament, which is a 4 player Round Robin. There is the basic Quad (with predetermined colors for players 1-4), and then the variant Quad where players in the 3rd round draw for colors. There is the Octogon, which is an 8 player (or less) 3 round Swiss. The Octogon and Quad are both tournament formats that are meant to have players of equal strength [approximately] play in 1 group. The advantage of an Octogon over the Quad is that there is less problem with dealing with an odd number of players, or groups not in multiples of 4.
The Holland System uses round robins in preliminary rounds to qualify the best scoring players through to a final round. Typically the final is a round robin among those who qualified. Those who didn’t qualify may play a Swiss System, or they may be eliminated from further play depending on how the tournament is structured.
There are two types of Holland System: Balanced and Unbalanced. In a Balanced Holland System the players are divided into groups of roughly equal strength. The winner, or top two, or top whatever the organizer decides then qualify for the finals. In an Unbalanced Holland System the top players are all grouped into one round robin. The next best set of players make up the second round robin, etc. Typically all plus scores in the first round robin, the top two finishers in the second round robin, and the winners of every other round robin qualify for the finals.
Prior to using the Swiss System, the US Open used the Holland system of round robins and a final as its tournament format. It took over two weeks to run the tournament and find an eventual winner. The 1948 US Open in Pittsburgh used the Swiss System. IIRC, the Swiss System was used earlier and was streamlined a bit by a USCF vice-President, Bobby G. Dudley, who ran a large event in Texas that became a model for others to use. I was told the 1948 event was based on that model.