amsdenj

Using the PC primarily with loading IRs into PC. I also like IRs loaded into Helix and some stock cabs and then running into PC FRFR.

1. I notice that once I save a preset on the Helix that has the PC as the output and IRs loaded into PC, that every time I bring up that preset on the Helix the PC remembers the settings on the PC(this is great). Should I be saving presets in the PC also? Only if you need to be able to use Power cab with some other modeler that doesn't have MIDI or Line6 Link control.
2. I am bringing most IR volume levels up on the speaker volume itself on the PC. Most IRs sound really good taking it up from the default -14db to around -12db- -10db. I am wondering if this is good practice, or should I be setting the volume levels in the amp channel volume and/or the output block on the Helix? Recommend gain staging and leveling your presets using channel volume, use output block set to -3dB and then set to 0dB with a boost switch, and get the amp volume from Powercab, not the blocks. This is simpler, easier to get consistent across patches, and allows you to reuse the same blocks in your Favorites in other patches.
3. I want to have some snapshots in a preset go to the PC with IRs and some snapshots to go to FRFR with IRs loaded on Helix. I notice I have to bump the speaker output to the +6db on the PC to get it to match up with the IRs. Should I be doing this another way? Its possible you'll need to do that, but generally IRs and cab models should be normalized to -18dB for consistency across patches. Note the big value of Powercab is to use the speaker models for amp in the room sound, and avoid IR or cab blocks in Helix at all. IRs in Powercab are best for HX Stomp to save a block.
4. Have not used the stereo spreader too much yet on the 212, but would like to. Not sure how I should set up presets to get the best out of that. I could just run a single signal path with one amp and choose a stereo effects at the end, or run two signal paths with two amps with mono effects and pan hard left and right, or run a single path and do a signal split and pan hard left and right. Not sure what is the best route to get big stereo field with delays and reverbs. For one amp, just follow the amp (or IR or cab block) with all stereo effects. If you use two amps, put them on different paths, and send one to the Left channel and the other to the Right channel of all following stereo blocks. This way your chorus, delay, reverb, etc blocks can be used for both amps and still retain stereo. But a simple way is to use different speaker models or IRs for the left and right speakers in Powercab 212. Gives you sort of the sound of two amps with only one amp block.
5. Can I save the wider stereo field in on snapshot and have it go back to normal in another snapshot? You can, but you might find the difference isn't worth it. Stay stereo all the time, Powercab speakers are too close together to have stereo/mono be that big a difference. For FOH, you're usually going to be mono all the time because stereo doesn't provide a consistent sound stage for people in different locations in the room. 
6. When I send a signal out to FOH, I would have to go from PC XLR Out to mixer? Since, if I were to go from Helix, without a cab or IR block because of using Speaker or IR in the PC, I am going to be sending a signal without cabs to FOH. So, if I am using a snapshot with FRFR and Helix cabs/IRs, and coming out of PC, then the FOH gets the cabs/IRs from Helix, if I choose the IRs in the PC, then FOH also gets the PC IRs or just the default speaker? (that was a confusing one, I know). The simplest signal path is to send the Powercab XLR outs to FOH. Then you don't have to worry about FOH having a potentially different sound than what you're hearing, and you don't need to have and redundant IR or cab blocks.
7. I have not explored how to use the PC just as a monitor on one of the speakers yet, not sure that I would. If I were to do that, I might just get a 112 PC. I wouldn't do it. Get IEMs and protect your ears and improve the quality of what you hear. Having a drummer behind you and a monitor in your faces is guaranteed to cause ear damage every time you play. Take it from someone who didn't pay attention to this, you will regret it later.