Mar66 212 is a great one too.

Yeah, it will always be neutral before you make changes.

ZERO latency. The only real latency is the FX Loop of the Eleven Rack, which is around 3-5ms I think (the official FAQ touts "less than one millisecond to process analog into digital" though).

NAD IR is good, their SHB-1 Bass plugin works great too. At least with the software, they can always make changes in post whereas the EPSI will be a little trickier.

I wouldn't use the EPSI outside of the Effects loop again, and make sure to use all four patch cables (not just two/another reason to utilize the FX Loop for this) and the stereo version of the IR if you have any stereo FX too. I always kept it in stereo with stereo IRs, last block in the FX Loop. Even if you track in stereo, DAWs can change that to mono in one click anyway so you can decide after the fact if it's not sounding better as mono or not.