Is the STINSON Softshell Vest actually waterproof?

It has a three-layer constructed membrane plus a water-repellent finish. That handles rain and wind well, but it is a softshell, not a sealed hardshell, so sustained heavy rain can still get through seams.

How warm is it compared with a fleece vest?

It adds wind and rain protection rather than insulation. Over a lightweight fleece it feels warmer than fleece alone, but on its own it is a shell layer, not a cold-weather vest.

How does it compare with the Maxson Softshell Jacket?

Same comfy softshell material and membrane, without sleeves. The jacket covers your arms in rain; the vest keeps your core protected and leaves arms free for movement.

What should I wear under it?

A lightweight fleece or a long-sleeve base layer is the intended pairing. It also fits under a hardshell as a mid-layer when the weather turns.

Does it run true to size?

It is cut as a men's vest meant to layer over a fleece, so if you plan to wear it over bulky mid-layers, size up. For a trim fit over a base layer, take your usual size.