Is it neccesary to have my audit done at the higher PCAOB level?
PCAOB audits are not required for your Tier 2 Regulation A offering, and of course no audit is requirred for Tier 1 offerings (although some States do require an audit).
However, PCAOB level audits are required for some of the exchanges (OTCQX, NASDAQ, NYSE) so if those are in the plan companies should use a PCAOB firm. Note that listing your company on the OTCQB does not require PCAOB.
PCAOB audits are more expensive than regular audits.