Absolutely. You can test as much as you like, but every roller coaster requires a break-in period (because, when you think about it, a roller coaster is just a bunch of new parts put together). Anyone who shows up to a roller coaster opening day expecting a fully functional ride with zero chance of failure is naive. MF and TTD are two extreme examples of prolonged opening troubles (TTD was essentially down half of its opening season), not to mention Maverick having to literally alter track and delay opening by a few weeks. Even simple roller coasters like Gatekeeper and Valravn had their opening troubles too.
It takes time, and everything gets sorted at the end.
For the question on 2 or 3 train operation; Cedar Point has yet to use the Steel Vengeance MCBR - it is totally deactivated with no brake action to be found. They could easily operate three trains, if they were to use the MCBR as an actual block. This weekend however, there was no sign of that intent, with stacking the whole three days through. So yes; two train operation works for Steel Vengeance. Once they iron out the kinks and get this roller coaster to regular operation however, I'd expect them to shift to 3 train operation, especially for its opening season, which would really eat through the queue.