I think the terpene card is currently being overplayed. It's opened the door to poorly defined misc stuff having terpenes added and then being sold as a specific strain. This confuses the already tricky picture.
Terpene vendors are making a lot of money, e.g. selling 2 ml of a mix of Terpenes (that they sell individually at ~ $10-30 for 30ml) for $25. Imagine if we bought them from chem lab vendors. And then we have the CBD vendors with their snake oil claims and pyramid marketing. It's getting predatory.
What exactly gives a strain its properties? the ratios of all the different cannabinoids, the ratios of terpenes, the ratios of flavonoids, and maybe that's it and maybe it isn't. Ideally terpene profiles alone would give some useful info, but even the honest measured profiles of different samples of (allegedly) the same strain vary a lot.
Personally I've found that going through many Leafly reviews with an eye for reports from users with some brains, and ignoring the dummies and the atypical reactions, gives me a good idea of what to expect. I'm trying to build up some knowledge as to which terpenes show up with the properties I like, but it takes time.
Some outfits like Dosist that seem to start with THC alone and then add a different terpene recipe for their various offerings, should be more repeatable. They publish at least the main terpenes.
Harborside in Oakland CA is planning to deliver a full analysis, with terpenes, for every unit they sell sometime next year. That will help build a better database. We'll get there ultimately.
