Both of them has time travel / traveling to a world with historical setting, with a clever MC who uses modern knowledge to solve crimes. Also great comedy and action.

Although Serendipity is more on the romance side and lacks the bromance that Spirealm has, both of the story bases are similar - in both shows they visit different worlds (VR games/books) with different settings, solve problems and find out about mysteries.

They have similar vibes with great plot, cool and fun MCs, both have a group of friends who learns to trust and rely on each other and tries to save the day. There is a bit of school setting, however in Tiger and Crane it is only a little part of the whole story.
Both ML is clever and strong, has a more mature and stoic best friend.
Also both female leads are great fighters and strong individuals.