Red numbers aren't too bad, as long as it's fairly close (maybe 10-15%?). Without mods, I can clear areas up to around 20% above my CP fairly easily most of the time, but that's with some relatively strong Nikkes on my team. Just don't go clearing an area with 30k expected CP using a team of 15k...
I've read a few times now that salted emails (+1, +2 etc.) are getting banned. Some are saying it's mostly less active accounts, ToS names, or seem likely to be mass generated by bots. No idea how much truth there is to any of it.