HeathCliff

Don't worry about the gear, worry about the shot. Look back in history at some of the greatest pictures made. They were done on gear that if far inferior to today's stuff. Some of my best portraits were taken using a $3 industrial lens with no aperture and lots of aberrations.

I owned the a6400 before and agree. You can look into the a6100 if reduced video capabilities and less-weather resistance is worth the price trade off. These two cameras feel like cheating when it comes out how damn good the autofocus is.
 
What I learned when I started is that you shouldn't really view the photos in 100% zoom. You're going to pixel peep and wonder why photos look so underwhelming. You should remember that YOU are the only person that will see these photos in such detail. Zoom out. Most people who look at your photos will only see your work on a 6-inch smart phone or some compressed version shared on Instagram/Teams/Discord, etc.

I'm partial to Peter McKinnon as far as YT creators go. If you want to read about cameras and lenses, Ken Rockwell publishes very extensive and detailed reviews.
 
I've been working in photography for about a decade, but my experience is much more journalistic, so it might not apply to you. Hopefully you can adapt some of these lessons.
Nowadays, largely, the camera body itself doesn't really matter. Modern cameras, even at the lower end, have so much technology from their high-end counterparts that they can produce amazing images. Like with everything, the features of the high-end market eventually trickle down to the lower-end: Xeon features trickle down to Core processors, for example. Learning the controls of your camera will do you much better than getting a better camera. Knowing instinctively what to change to achieve the image that you want to get without having to think about it will make your images better. You'll be able to fire off the shot far faster than if you're sitting there, fumbling with the settings, by which point the subject will have moved on. Learn the exposure basics, learn what features of your camera affect the quality, learn what the limitations of your camera's body are (dynamic range, sensitivity limitations, low-light limitations), and actively work against them to find its advantages. Glass matters. A lot. My one key lens (again, minding that I work in sports journalism) is the 70-200mm f/2.8. That lens, while expensive, has the durability to be handled by pros on a daily basis, getting banged around, dropped, rained/snowed/sleeted/hailed on and so much more. It's also  a well crafted assembly, featuring a metal construction and quality glass. The performance difference between a $300 lens and a $3000 lens is far larger than the performance difference between a $500 camera body and a $5000 camera body. For travel, I'd probably go wider. Somewhere in the 14-85mm range is a good place to look for focal length (essentially, the zoom). The pro-level versions would be the 14-24mm f/2.8 and the 24-70 f/2.8. Find something in these ranges (the kit lens with many entry-level cameras is an 18-55mm f/5.6) and learn what its focal length characteristics are and how it handles. Your photographic style might be conducive to using prime lenses (lenses that only focus, their focal length is locked). A quality 35mm, 50mm, and 85mm set isn't too expensive, but these lenses are incredibly versatile and produce very, very sharp images. Brand doesn't matter (as much). Where possible, I like to stick to first-party lenses (rather than the third-party Sigma, Tamron, or Rokinon lenses). They maintain their value better and don't experience nearly the same number of "weird" issues. However, the debate between Canon/Nikon/Sony/Fujifilm/Panasonic/insert-other-brand-here isn't really as big as some people make it out to be. That being said, many photographers will stick to what they started with, and their entire collection of equipment will be from a single brand. The pieces will all play nice with each other, and the controls and feel of the cameras and lenses will be familiar. Front lens caps can sod off. They get in the way and are generally just a nuisance. The only place for a front lens cap is when a lens is going back in the bag. Don't keep lens caps in your pocket or attached to your camera. Just leave them in the bag. Rear lens caps and body caps are far more important. Keep the inside of your camera clean, and always cover when not actively switching. Lens hoods are a good idea. Not so much for flares, but simply for impacts to the front of the lens and to protect the front element. If you have the camera over your shoulder as you're traveling, you'll bang the front of the lens around naturally. The lens hood will take a lot of those impacts and break before the lens does.

First thing I'd do is check to see if the memory ICs are the same across all sticks. Just because two kits have the same model number doesn't mean they have the same memory IC installed on them and can be incompatible. If you bought this as a 4x16GB kit, this isn't applicable, those are validated to work together, but assuming you bought this as 2 2x16GB kits this would be the first thing I'd check. You can do a quick and dirty check right in CPU-Z by going to the SPD tab and looking where it says DRAM Manuf. and double checking to make sure that it says the same thing across all the memory slots, or you can do this the more granular way by downloading a program called "Thaiphoon Burner" and reading the SPD of each DIMM, doublechecking that the Die Density / Count box is the same across all DIMMs. Even the Thaiphoon Burner method is subject to error, but it's not that common. 
 
While you're doing that, do doublecheck the organization of each memory stick, you want to find out if they're single or dual rank. If you're running 4 dual rank DIMMs, that puts a ton of stress on the memory controller and could cause you issues at 3600MT/s. If you're running 4 single rank DIMMs, that's not really an issue and should be OK. 
 
Anyway, after you've confirmed that the memory is all the same, start trying to see if adjusting the SOC voltage helps get this stable. It could be that your 5800X3D has a pretty weak memory controller, and since it runs off the SOC voltage raising that to 1.15V might help get this to be stable. 1.2V is the max you'd want to run for daily operation, though the majority of Ryzen 3000/5000 series CPUs sweet spot somewhere between 1.1V and 1.2V for stability, hence the 1.15V recommendation (my chip personally does best at 1.175, but your mileage may vary), it's "I don't feel like fine tuning" voltage. If that doesn't get it stable, still leave it there since it can't hurt anything, and try seeing if increasing the DRAM voltage slightly will help. 
 
If neither of those help though, I'd just start dropping DRAM frequency until it does work. Realistically the 5800X3D doesn't really care about memory performance much, if at all, so the difference between 3600 CL18 and 3400 CL18 is going to be basically impossible to notice.

Uhhh, first?

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Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.

Aah yes, west Taiwan is getting salty again.