Whether you check your bags curbside or at the check-in counter makes no difference as both are pre-Security.

In any event, you will likely not be able to OLCI as UA will do a document check first. Whether OLCI works is determined by UA's algorithm which appears to largely focus on how recent your last document check was.

As a practical matter, I would much prefer to check the bags at a counter and do the document check at the same time. If there are any hassles, it is better to keep everything together.