No — the theme only describes the art and story, not the mechanics. Museum slots on this site come from Genii, KA Gaming, each with its own RTP, volatility, and bonus features, so it's worth checking a game's own stats rather than assuming from the theme alone.
Museum of Fantasy Fusion Reels by KA Gaming has the highest published RTP among museum slots on this site, at 96%. Not every game in this theme has a published RTP, so this reflects what's actually disclosed, not the full set.