Yes. The Cropped Racer’s side pockets fits most phones, so you can carry it without a belt or vest.
No. It has a built-in bra with removeable pads and medium support, so you can wear it on its own as a running crop top.
Yes, as a base layer. Wear it under a jumper or jacket, and use the pockets for gels and keys.
A running crop top is built for movement over distance: it stays put, wicks sweat and often has pockets. A sports crop top is a broader term that covers gym and studio styles too. The Cropped Racer works for both.

