Learn Finnish: Minkälainen on seuraava akrobaattinen esitys? - What kind of acrobatic performance is next?

Both words mean "what kind of" and are largely interchangeable here. Millainen is slightly more common in standard language, while minkälainen is formed from minkä (the genitive of "what") plus -lainen (kind of). You will hear both, but minkälainen can sometimes feel a bit more colloquial.

Why is the verb on placed right after the question word instead of after the subject?

In Finnish questions, the interrogative word (minkälainen) must come first, and the main verb usually follows it immediately. Even though English puts the noun phrase first ("What kind of acrobatic performance is..."), Finnish naturally structures this as "What kind is the next acrobatic performance?".

Seuraava means "next", but does it come from a verb?

Yes, it is the present active participle (a verb acting as an adjective) of the verb seurata (to follow). So literally, seuraava translates as "the following".

I see akrobaattinen ends in -nen. Does this behave like other -nen words if the case changes?