You are on your way. I have 2 RGB high end builds that use In-Win 909's.
Things to consider while you are asking your questions:
1) RGB there are two forms of it. 5v Addressable and 12V what I call "Slave" RGB. The difference is the 5v addressable tells each light what color to be while the 12V "slave" RGB tells all the lights on the bus what color to show with no differentiation. They are not interchangeable and could blow stuff up if you try to use a 5v in a 12v header.
Something to know as well. ASUS uses a 4 pin connector for both 5v and 12v RGB headers. Just remember that the 5v version of this connector only uses 3 pins of the 4 pins. There is actually a blocking key built into the connector to keep you from using it on a 12v RGB header. Just looking at the connector can be tough to tell until you see the blocking key.
The case 805 infinity has out of the box a 4 pin 12v header cable for your 12v "SLAVE" RGB header bus on any of the latest ASUS MB's unless this has changed and it specifically says 5v addressable headers. If it's the 5v addressable then you would use an addressable header on the ASUS MB instead.
The Fans: If you go in-win for the fans you will want the Crown or Aurora fans (Crown looks the best). You might want to look at Sirius loop fans from In-win too. I think they just came out and off of the listed fans use the 5v Addressable RGB header. They also have an all in one splitter cable used to connect the fans to a fan header for fan control and a 5v RGB header for the MB connection. It condenses the cables down to one. They can then be daisy chained inside the case for easy cable management as you pointed out. If you go outside and look at Thermaltake or corsair you will then move onto those eco systems and will have to run the fans and control their lighting using their software. This means you will need to load up their software to control them instead of being native AI Suite / AURA SYNC with ASUS.
RAM: You can never go wrong with gskill tridentz RGB. Aura Sync compatible and an extremely good memory product.
The AIO is something In-win doesn't have. I have a Ryou 240 and recently a Ryujin 360 for my newest build. Before these, I had one of the early NZXT Kraken X62 RGB coolers. It's very nice as well but takes NZXT CAM software to control it which is pretty bloaty and does interfere with sensors at times. Something to consider as you will be loading their control software if you start moving out of the ASUS eco system.
The graphics cards are just plug and play. If you go with ASUS they will automatically connect to the lighting system of the ASUS MB and be controlled by AURA SYNC. Nothing to really worry about there. As far as the bridge goes I have seen it just about everywhere.. amazon, Newegg ebay etc.
Power Supply: In-win really doesn't have a good RGB version here. They have some lights on specific supplies generally built for their premier cases and not for sale otherwise. There are some alternatives. As you may know, ASUS has the Thor 850 supply with built in RGB and OLED power draw readout display. I just bought the 1200P for my latest build. It's asus and pricey so pick whatever rgb supply you like. You can also light up the power supply shroud area with a LED strip too if you wanted. Just a thought. There are a few brands with builtin RGB.
As far as the usb 2.0 connections are concerned you will need them. In this case, I think you will only need 1 connection if you stay ASUS on most parts. Other items that use USB 2.0 MB connections are larger fan products that come with their own eco system ie: Thermaltake, corsair etc, anything with an RGB interface that takes control outside of AURA SYNC like corsair lighting node pro etc. In your case, it sounds like the only thing that would need the USB connection is which ever AIO CPU cooler you choose. Remember non ASUS you have to use outside software to control them.
Fans like In-wins are designed be controlled by the MB or 3rd party fan controllers "PWM". You get controllable (PWM) and Full Speed (FS) fan headers naturally on the ASUS MB that are controlled by Fan Expert that comes with AI Suite. It does a great job in my opinion for standard builds such as yours.
How to hook it all together is based on what you bought. Videos on YouTube are good at seeing how products work and what their pre-requisites are. So from what I am reading here this is how I see you putting this together:
Depending on MB you can get as little as 1 - 12v header and no 5V header eg: GENE. But for the most part, you get at least 1 of each RGB header. Some boards give 2 of each RGB header. You will also get at least two USB 2.0 headers on an ASUS MB. So this is how I see it making assumptions.
CASE: 1 - 12v RGB header on MB
Fans 5v RGB header, the number of 4 pin fan headers on MB should be sufficient.
Graphics cards: Self controlled and managed by the MB
RAM: gskill tridentz rgb self controlled and managed by the MB
AIO RGB CPU Cooler: ASUS just needs USB 2.0 header and ASUS normal software. Other Product you will need USB 2.0 header and supporting 3rd party eco system software.
Power supply: 1 - 5v addressable RGB usually.
Now if I missed something or if you use different parts you may need more connectors for 5v RGB. There are extension splitter cables for both 5 and 12v RGB connectors. You will need one of those if you don't have enough headers on the MB. Same thing goes for additional USB 2.0 headers if required. NZXT makes a nice 2.0 hub for the MB connection that fills that gap. Sorry this is getting long so ask any questions you might have..
InWin 909 Silver RGB build
i9-10900k
ROG Maximus XII Apex
ROG Matrix 2080 ti
Gskill Trident Royal 4400 16g
Everything overclocked and love it.
ROG Awesomeness !!!!