AMD's chipset naming convention is mostly nonsensical and fairly misleading.
The B650, B650E, B850, and X870 are fundamentally the same thing...a single Promontory 21 chip.
The X670, X670E, and X870E are also fundamentally the same thing as each other...two Promontory 21 chips, with one daisy-chained to the first, meaning all that extra I/O still has to go through the same x4 PCI-E 4.0 link to the CPU.
There are some largely arbitrary nuances that separate the different chipsets...mainly how much PCI-E 5.0 is enabled vs. 4.0, while the 870 and 870E technically need to include USB4 (on a separate chip) which eats up four PCI-E lanes, often leading to the irony of the B850 boards having the largest number of usable CPU attached M.2 slots that don't steal lanes from the GPU.
There is also a mild trend of the 800 series boards having better memory overclocking than the 600 series, as they've had to pay more attention to trace routing and the like to get official 8000MT/s+ support. This is just a trend however, and not an intrinsic property. Older memory-focused boards (e.g the ASUS X670E GENE and Gigabyte B650E Tachyon) will beat the overwhelming majority of X850/870/870E boards in peak memory performance and it takes a high-end quad-DIMM board to match mainstream two-DIMM (mostly ITX) boards, regardless of chipset.
Personally, I don't pay too much attention to the chipset itself. I do stay away from A620 and B840 boards as they have most OCing features disabled for market segmentation reasons (and are generally very low-end regardless), but beyond that I look for the minimum I/O I require, then pick the board that seems to have the best combination of relevant OCing features (advertised peak memory speed, number of PCB layers, VRM topology, general clutter) and firmware (how frequently it's updated, what AGESA versions I can find if I don't like the newest one, what settings are available [things like being able to disable certain hidden limiters, set different tRCDRD and tRCDWR timings, being able to tune VRM switching frequency, et al, are nice to have], etc).
Anyway, when selecting a board you want to figure out what you're going to attach to the board, then take a careful look at the manual (especially the block diagrams, if their is one). This is how you avoid unpleasant suprises like knocking your GPU down to 8x or not being able to use SATA ports if you want to use all your M.2 slots, or not having any rear USB ports that aren't routed through multiple layers of hubs.
