You're welcome.
Thanks. I'm certain with practice, patience, and perseverance you will get to where you want to be.
What do you think the Z7 and 24-70/4 will do that you can't do now? I just now read Thom Hogan's review of your 10-20mm lens, and what stood out to me was where Thom wrote, "I was reminded of my late mentor, Galen Rowell, as I used this lens. I'm pretty sure that a D3500 and a 10-20mm AF-P lens would appeal to his 'go anywhere' adventuring style. The two form a highly competent image quality capability in a very small/light package."
My experience with my D800 and Sony A850 before that has been that getting good corners is harder on the larger format. I have and use a tripod, and I consider that to be the most important piece of gear for good landscape (and macro) photography; but I often get excellent results handheld with my D500 and Tokina AT-X Pro 14-20mm f/2, and that's something I have almost never been able to do with FX/"FF" cameras and lenses.
Dynamic range just isn't much of an issue these days. I remember dealing with that issue with my D300 some, but even then it was manageable. Even now it comes up infrequently with my D800, but I get around that by taking two shots about two stops apart, one for the highlights and one for the shadows, and then blending them (often I just take one ETTR shot and do two conversions of it and then blend those for an excellent result). The resolution I get from my D500 is perhaps 95% of what I get from my D800, and adding more megapixels has diminishing returns; OTOH, compared to my D500 I would quantify what my D800 can do in terms of fps, acquisition and tracking of its AF system to be about 75% -- so when push comes to shove I'll take my D500 over my D800 -- YMMV.
I doubt the D500 is "hugely" better than the D7500. If you can get a D500 for less, even if it has a little more use, I wouldn't hesitate to do that. My experience with my D500 and D800, and before those the Sony A850, Nikon D300 and D200, and D70 has been they all feel pretty good with the lenses I've used on them (the D70 doesn't have a way to lock-up the mirror, so I considered that and its 6 MP of potential resolution a dealbreaker for serious landscape work; and the A850 placement of the AF-On button didn't feel comfortable to me, so that made it less enjoyable to use for me). I would say the size and weight of these camera bodies becomes more of an issue if you are carrying more than one of them around, but I will use a shoulder strap to carry my D500 and Nikon AF-S NIKKOR 70-200mm f/2.8 VR and carry my D800 with a two pound T/S (tilt-shift) lens attached to my tripod slung over the other shoulder and with a backpack carrying three more T/S lenses in it, and even at 61 y/o I am fine if I don't have to race to get somewhere (sometimes I do end up racing when I want to be somewhere specific before the light goes away).