ZHA vs Z2M
My take on it is here: ZHA Vs Zigbee2Mqtt - #3 by jerrm.
Both have some OTA support, z2m is probably better, but the latest zha toolkit can now use the z2m OTA repository, leveling the playing field, even if not fully GUI integrated.
Sonoff WiFi Bridges
I’ve seen mixed reviews on the Sonoff WiFi bridges, but have no first hand knowledge. If you must go WiFi and you’re OK with flashing, they may be OK. Ideally use something wired like Coordinators | TubesZB Store.
The difference between the two models is the chipset. The original is a Silicon Labs chip, the “P” is the TI cc2652 chip. For ZHA either should be OK. Theoretically both are supported by z2m. but the SI Labs chip is still marked as experimental in z2m (but there is some current discussion about removing the “experimental” label). For Z2M I’d get the “P” version since the 2652 is what the z2m developer uses and will likely remain the best supported.
Also, If you have a spare Raspberry Pi , similar SBC, or other always-on pc, you can run a USB dongle (or even the full z2m container) remotely from it as well.