I'll have to take Miguel's concepts he mentioned above even further. Except for one exception, my gear choices are (or would be, more on that below) pretty much brand-agnostic. I've tried others, but stuck with those that worked for me, regardless of the stickers on them. I'll not list every last item here (there are a few "pockets of resistance" in the gear cupboard that haven't been moved on and will probably stick around for no good reason), but this is why I have and keep what I have:
To tick off three "brand" that haven't been relevant to my decisions, my three fixed-lens cameras are all on-of-a-kind options that occupy their respective niches through their specific assets: Canon G1X III: reasonably good zoom lens, proven weather resitance, very nice handling with a great set of features; Fujifilm X100V: bright lens with great optical performance, RF-like gestalt and handling, reasonable weather resistance; Ricoh GR III: tiny size, stabilised sensor, truely impressive lens. Actually, I've tried to convince myself to let go of the GR III countless times by now due to its lack of something I really want in a camera, a reliable viewfinder of some sort. But the size and the lens (in essence, the results I can get from it) have so far made me keep it. In essence, I wouldn't know what to replace it with (though the Canon G5X II comes close - but ... that lens!).
Next on the list is

- there are nostalgic reasons involved here because it was

that made me really enjoy digital photography for the first time (the small and pretty stylish, if frugal Olympus PEN E-PM1; I still miss that camera, but I actually broke it ...). The nostalgia is mostly served by me keeping a Panasonic GF1 around - still a surprisingly capable camera with good, if not perfect handling; the add-on EVF is pretty ridiculous in terms of quality, but at least it's small(ish) and helps with framing. The GX9 is my "auto Leica" - an RF-style camera with all the necessary features to make shooting quick and effortless; that said, it's limited by its less-than-impressive EVF and mediocre I.B.I.S. - but at least it
has all those features, and they're certainly adequate. I owned a Fujifilm X-E3 once and enjoyed a lot about that camera, but the GX9 had it beat in terms of operational speed and versatility, and then some. Paired with a small prime (usually, the Panasonic 15mm f/1.7), it's a pleasantly small package that also packs a punch. Miguel has already described the assets of the Olympus OM-D E-M5 III - together with its 12-45mm f/4 PRO stablemate, it's my preferred compact bad-weather combo, but it really works in almost all conditions, and it's also a capable night shooter due to its fantastic (if no longer class-leading) I.B.I.S. All in all,

is a compelling small system for me - it's no longer state of the art in some respects, but those don't matter because still, great things come in small packages. And familiarity also goes a long way here ... Still,
if I should decide to further reduce "system" count, it's

that'd have to go. No need or reason for that yet, but that may change.
Now for the
brand in the game: Nikon. I've been a Nikon shooter pretty much from the day I began to take photography seriously (some time in the mid-80s), I know my way around Nikon cameras, have lots of gear and find it very satisfactory in use and in terms of quality. That's it, really. However, my Z bodies and lenses now also represent the core of my photography gear - they pretty much top everything else I have (and have tried) in terms of handling and results, i.e. as a complete package. That goes for the FX bodies as well as the DX bodies; each of them also brings their unique qualities and technical assets to the table that makes me enjoy using them. At the moment, I think the Z f meets my personal needs best: technically powerful (best I.B.I.S. I've ever used, best 24MP sensor I've ever used, fastest AF system I own), small enough, stylish enough and very sturdy as well as fully weather-sealed - a definitive win. The Z 7 II still handles even better, and its wonderful sensor and confident performance make it a superbly reliable package that really doesn't lack any major quality or asset I could want or need (that said, if a Z 6 III - yep, Z 6 - with the Z f's innards comes out, I'll have to think about replacing the Z 7 II because, in spite of the greatness of the sensor, I rarely need its resolution). The Z 50 is my favourite travel zoom and long lens Z body due to its solid sensor and 1.5 crop factor - but its main strength is its fantastic handling in spite of the small size. The Z fc is light and fun to use with small or even tiny primes - even though it has been kind of superseded by the Z f in term of handling and performance, but: My whole four-lens travel setup for the Z fc isn't much bigger and hardly heavier than the Z f with a single prime ... Finally, the D750 completes the system (and serves my nostalgic needs as well) by being equipped with a focus motor. Even though by now, I'm a bit put of by its bulk (in spite of it being one of the smallest FX DSLR bodies Nikon has ever produced), I still like pairing it with longer lenses/zooms as well as older (screwdriver) AF as well as MF lenses. The pentaprism is still something to behold, and its AF system remains solid and reliable. btw. All my FX bodies also share batteries - very helpful in a pinch, and also one of the reasons I haven't replaced (and won't replace) the D750 by the Df (handling considerations are in play as well) that would otherwise be my choice for its prowess with older lenses. But the D750 gets so many things right that it'd be foolish to exchange it for a body that lacks many of its capabilities. Though what Nikon really needs is an "FTZ" adapter with a built-in AF motor ... (yes, I read about the E-to-F adapter with a built-in motor, too.)
Here's a little oddity: I also keep the Nikon 1 V1 around - because it's the epitome of "enough": It's
just small enough to not take up enough space to be in the way, it's big enough to handle
just well enough not to be too fiddly; its sensor is
just good enough, its small lenses are
just good enough (with the exception of the 18.5mm f/1.8 which is really good). It kind of serves as a "lower boundary" for what I could still work with if anything else had to go ...
Finally, there's also the elephant in the room: Why Leica? Because there's nothing else like it - the experience (as well as the results) are unique and, to me, absolutely worth it. To me, this is photography pure and simple; I'm neither a fanboy nor a zealot (I really couldn't care less about the badge), but if I have the time to really immerse myself into photography, there's nothing that suits me as well as one M body and one carefully chosen prime for that purpose. I love every aspect of the experience, down to the many limitations - they're all irrelevant compared to the sheer joy I get out of using that system.
I'm passionate about user experience as well as performance; settling on a clear route took a lot of time (and quite a few futile attempts and much back-tracking). But I've pretty much arrived at a state of affairs I'm truely happy with. I'll remain an experimentalist at heart, but there are no major shifts on the horizon.
M.