I've updated HiveOS to the latest kernel and all the other applications so that I'm running the full-spec HiveOS release (standard libraries and drivers), and I'm still getting random timeouts on the AMD cards.  I'm getting the same timeouts on windows using a 3070Ti and 6900XT with 1000 watt platinum PSU, so I can be pretty certain it's not a power problem, unless there's some issue in the power being supplied from the mains (I should probably check to make sure I'm getting consistent voltage and it's not browning out -- but it's not always the same cards at the same time -- but the wiring is kinda weird since it used to be 220/240V and was converted to 120V).

I'm running the 3090 Ti now too.  It takes different timings on the memory (higher stock values than the 3090), but can be run up to 11851+ MHz and still be stable (although this is +2700 in HiveOS offset which wouldn't break 10000 MHz on the 3090).
As for speed -- it's faster for sure, and with some tweaking of the clocks and voltages it's not any more power hungry than the 3090 in software reporting anyway).  Right now it's running between 138 and 155 MH/s, but the memory temperatures are WAY WAY better than the 3090 -- 58 vs. 84 Celcius at 328 watts for both cards, so they're much better for a farm since there's no memory on the back-side of the card to cool.

I'll continue to tweak the 3090Ti, but I'm currently running at 85% amperage capacity of my wall power, which is not advisable, although as I said, the original wiring was rated for 220/240, so it's more just an issue with the breaker possibly tripping if I try and push too much more power through the circuit.