Terrain should be chosen before top speed. Surface conditions determine how much traction, ground clearance, tire volume and drivetrain capability a vehicle needs.
Pavement
Lower-profile tires and predictable steering matter more than extreme clearance.
Grass and loose dirt
Ground clearance, tire diameter and four-wheel drive can become more important. Small vehicles can lose momentum in tall grass.
Sand and mud
These surfaces increase load on electronics and bearings and demand careful cleaning. Water resistance does not mean maintenance-free use.
Rocks and crawling
Low-speed control, gearing, tire grip, articulation and approach angles usually matter more than maximum speed.