Small speculative unprofitable growth companies outside the major indexes are usually always the best performing stocks, because stocks in the same category are in the list of worst performing too. They have huge volatility.
Why would you use the market cap as a measure for large when we're discussing overvaluation? It seems like more fundamental measures (revenue, earnings, market share) would be more appropriate.
Tesla has 10x’d from a year and now at a $420B valuation. That makes it one of the largest companies in the world (I believe top 15)
All the companies that fit in this category like Carvana, Wayfair, Overstock etc are now at $10B-$30B valuations.
Point is these are not small by any means.