I'd definitely take the opportunity to make sure the BIOS is up to date (just to be sure you're running one that supports the newer CPU), or just default everything if you're already on the current version before pulling the 5600G and dropping the new one in. Then after you've confirmed the board recognizes the 5700X3D it's just a matter of changing your settings back and dialing in the memory timings.
I know it's tedious, and probably not strictly necessary, but I figure it's better to start off with a clean slate whenever you swap out a CPU or reconfigure your memory, just so something you didn't think about doesn't come back to bite you later on.
I usually just go through all the BIOS screens where I've made changes and take photos with my phone, then use those as cheat sheets to refer back to.
FYI unless you're planning to manually tune that memory to a lower speed, DDR5@6800 isn't really feasible on AM5 at the moment. 6000MHz is the current sweet spot, and even getting that stable is much easier to achieve with 2x16GB modules.
You get the same types of choices that you get in the first two games, but it's really streamlined. And you can absolutely murder/spare people as you see fit because it doesn't really affect the outcome. There is an achievement for clearing a single level without killing anyone, but not one for the whole game.
I didn't even realize there wasn't a chaos system until I finished the first level. I still played my usual way on that first playthrough, though (ghost/clean hands). On the second run I murdered everyone. Third run was the Original Game+ (where you get to use some of Corvo's and Emily's powers instead of your own)... that one was actually the hardest because Billie's powers are honestly better, at least in this one.
The only thing I've never really done in these games is go with the combat-- I'm purely stealth. I know the combat is amazing and completely open-ended, but I honestly suck at it.
I absolutely love playing stealth in games that let me take that option. My preferred route in the Dishonored series is low chaos/ghost because of how challenging it can be, but I always reload saves to get though them because I like to experiment to see what works (and what doesn't), and also because I honestly just suck at getting things to go the way I want them to sometimes.
However, even though low chaos is apparently canon, I would like to point out that a stealth high chaos run where you murder every last guard/thug/weeper from the shadows can be sublime. Shadow Kill helps immensely here because when they dissolve into ash there are no bodies to hide (though half of the fun for me is finding out-of-the-way hiding places for everyone I've choked out and/or murdered).
And while it doesn't have nearly as much replayability because it ditches the chaos system entirely, Death Of The Outsider is loads of fun simply because you can literally do whatever you want, without having to worry so much about the consequences.
I'm also of those weird people who really likes the second game, too... maybe even more than the original, though they're both basically equal to me. Really don't understand the hate that one gets from some fans.
Should work fine. You'd just have to set the timings manually to run them all @3200 (one XMP profile runs at 3333MHz, while the other is set to 3200, even though the main timings and voltage appear to match otherwise). Or if you didn't want to bother with setting everything up manually you could probably run both with the second profile, which is 3000MHz on both kits.
Four sticks is usually harder on the memory controller than two, but you wouldn't be pushing high clocks on the memory anyway, so you'll probably be fine. That said, a new 32GB kit would be simpler in the long run, even though it's cheaper to just add a second kit.