Performance should be almost identical between SD835 devices and not a single SD835 device uses 32bit support, they're all 64bit.
In regards to the controller, while a first party mod is nice bluetooth controllers shouldn't have latency anyway. Also your controller lacks two shoulder buttons which may be a problem for some games (for example I get round the lack of analogue triggers for Mario Sunshine by mapping Z to LB and light press R to RB).
Overall the Z2 Force is a good choice for Dolphin, same as any SD835 device. But the Galaxy S9 is out with a SD845 in some markets and there should be other devices with the SD845 in the coming months, so they should be the best you can get at the moment. But I'd expect it to still be a subpar experience with no big improvements or anything.
In regards to the controller, while a first party mod is nice bluetooth controllers shouldn't have latency anyway. Also your controller lacks two shoulder buttons which may be a problem for some games (for example I get round the lack of analogue triggers for Mario Sunshine by mapping Z to LB and light press R to RB).
Overall the Z2 Force is a good choice for Dolphin, same as any SD835 device. But the Galaxy S9 is out with a SD845 in some markets and there should be other devices with the SD845 in the coming months, so they should be the best you can get at the moment. But I'd expect it to still be a subpar experience with no big improvements or anything.