Learn Finnish: Kirjailija tapaa vaellella puistossa. - The writer tends to wander in the park.

Yes, its most common meaning is "to meet". However, when tavata is used as an auxiliary verb followed by a first infinitive—in this case, vaellella—it means "to have a habit of" or "to tend to". This is a common way to express customary actions in Finnish.

Why is the verb vaellella used here instead of the standard verb vaeltaa (to wander/hike)?

Vaellella is a frequentative derivative of vaeltaa. The -ella suffix indicates that the action is casual, continuous, or aimless. While vaeltaa often implies a hike or a journey with some direction, vaellella perfectly captures the feeling of strolling or wandering casually around a park.

Does tavata conjugate differently when used as an auxiliary for habits?

No, it conjugates exactly the same way as it does when meaning "to meet". It is a verb type 4 word that undergoes consonant gradation from 'v' to 'p'. So tapaa is the 3rd person singular form for both meanings. You can tell which one it is from context: if an infinitive verb directly follows it, it is the habitual auxiliary.

Can I express this exact same meaning without using tavata?