Personally, use the edit software first. For me it made using the unit without a computer way more easier because I could see the whole layout, menus, and understand how the device worked conceptually so that when I was scrolling through endless menus I could still visualize what it looked like on the computer screen. Lots of great suggestions but I just got mine a month ago and here is what I wished I knew up front as someone who has used a ton of plugins, a helix, a Neural DSP, and Kemper to name a few and still always went back to tube amps.
1) If you use an FRFR the global setup output eq is your friend to help shape your specific sound to the particular FRFR. My FRFR went from sound like hot garbage to amazing. Borrowing from Leon, I did a 12db cut at 80 and a high cut at around 9800 plus a small notch at around 250-300 to get rid of that boxy sound.
2) OMG 9 is your friend if you bought the FM3 with the FC-6. Download it and install it now
3) If you are running the unit into a tube amp and cab of course don't use the virtual cab but also toy around with the amp unit under the speaker menu and adjust the cab resonance according to taste. Depending on my cab I have it off (4x12) but on a 1x12 I might have it on to give the 1x12 a little mid low beef.
4) PlexDly is your friend. It is both a reverb, shimmer verb, and delay.
5) Create and save amp presets yourself in the library tab. That way if you have a favorite amp setting you can load it straight into the new preset instead of trying to recreate it tweaking 20 different parameters.
6) IRs can make or break a sound when using an FRFR or recording direct. While one IR may sound magical for one amp, it might sound terrible for another!
7) Volume matching before practice or live shows will be your friend. Get a DB meter plugin for your phone and match your presets
8) Watch the forums...there is always a useful post almost every day for new users.
9) The wish list is your friend. Post if there is an amp, or pedal you are looking for. Even the designers will respond when you ask for the oddball shimmer pedal and others will help to try to come as close to the sound with what exists as you can. While nothing in the FM3 can quite replace my Flux effects Liquid Ambience pedal, with the help of the users and some of the designers I was able to come close enough live. Will still use the flux when recording, but I actually believe if I sent the flux into fractal they would figure out a way to put it into the next update.
10) Scene controllers are your friends. They are a little awkward but it makes sense if you change the delay time in one scene you change it in all because it is similar to a analog pedal board. So you can also change delay time per scene per preset by using the controllers/scene controllers so that the thing you want to change per scene (say delay mix and volume) can be done using scene controllers instead of channel variations although channel variations is another way to do it. However, you get more seamless changes with scene controllers.
I could go on but I will stop there. I have had a blast with the FM3 and I really shock people with how amp like it sounds. I liked the Helix, but this thing can do so much more. Maybe that is my last bit of advice. Don't stay up to 5am tweaking the amps sounds for three days in a row. At some point just play guitar and have fun.