To my understanding, couldn't you have 4 DIMMs on the 8 channel CPUs? Obviously not using every channel though. Not that it would make a lot of sense, but just because you have 8 channels, I don't think you have to fill them for the system to work. Kinda like when some ppl back in the day would use a dual channel kit of 2 DDR4 DIMMs on their X99 boards.
But yeah, I would probably want more lanes as well, so 3435X might be the one. I wish there were also more motherboard choices. Though, it seems like Emerald Rapids isn't too far off, at the very least I would wait for that. My current CPU is doing fine for now.
And I actually have been using HEDT off and on for quite some time. I have had X58 boards, an X79, and the X99. The X99 is currently in my TrueNAS, and the X79 I gave to my sister.