NFS has become an unmoderated disaster.

I checked out some of your videos and have two things to saw. First is that you seem to violate the "show, don't tell" rule pretty hard. I would expect videos about EDM to have at least some music in them. You ask a lot of your audience to get excited about a genre or a subculture without ever revealing its principal self. Second is that documentary, like narrative, is really story driven. Your videos assemble strings of interviews. The interviews may seem like stories in the minds of the people who are giving them, but they are not THE story. If you watch the documentary GOOD COPY, BAD COPY (and perhaps relevant to your interests, the section about Tecno brega), you will see the craft of making a larger story from a set of story elements.

The GH5 is amazing, but don't forget that video monitoring is also an important part of the kit. The Atomos SHOGUN recorder/monitor provides a great monitor with helpful tools (focus, waveform, vectorscope, LUT, etc) that allow you to really optimize your image capture. Without an external monitor you have to use a screen that's too small, with focus peaking that's too generous (to the camera, not the image).

You should also audition the Blackmagic camera for its color quality. I never liked BM's color. I do like GH4/GH5. Color is very much a matter of preference, so really important that you like the color you are buying. LUTs can only do so much...

The original SHOGUN (prior to the Flame) would be a much less costly upgrade than trading out a GH4 for a GH5. As well, the SHOGUN records file formats that are more NLE-friendly. (The GH5 produces files that only the studio version of Resolve can read, not the free version). The OP doesn't say whether they have other monitoring tools for focus, waveform, etc., but the SHOGUN makes it so much easier to hit good focus, find good exposure, etc., compared with the tools native to the GH4 (or GH5).

Of course if you need to put your camera on a gimbal, then the external monitor changes things a lot. But if you are recording on sticks, I'd recommend the SHOGUN.

In the spirit of neighborliness, I just wanted to say "thank you" for doing such a good interview with the director of this great documentary. Keep up the good work!

^ Junk answer. That list of digital cameras is NOT for filmmakers. It's for people who think they want to read some reviews before dropping almost no money on consumer electronics junk.