Re: Transaction Cache vs. DB Cache Questions
Good question and I do not know the answer. Indeed, the documentation suggests that the DB cache stores less information than the transaction cache, but it is not explicit about vertex properties. It is not explicit about vertex properties in the transaction cache either, but I cannot remember users having problems with missing vertex properties there.
TinkerPop/JanusGraph support multi-threaded transactions. When using these (maybe, you already suggested this in your final line), you are sure that vertices are available from the transaction cache, provided its configs match your traversal.
Best wishes, Marc