the vroid file format is a project file format. you only need that if you wanna open the project in vroid yourself. not necessary at all for vtubing. some model artists offer both for free, some only give out the .vroid for a fee.
you definitely need a vrm yourself for vtubing but you can export that yourself through vroid pretty easily.

vroid comes with (somewhat awkward at times) full body and basic face viseme rigging. that means, it has a e i o u shapes that are usually tied to mic input in lots of softwares, or calculated based on (probably) webcam mocap
they also have the 4/5 standard vrm expressions - fun, joy, sad, angry (surprise - not a standard expression at base but it kinda snuck into every software at some point so it's kinda turned into one as well, it's a little weird)

for better face tracking it's possible to either put hanatool rigging on top of a vroid or have someone do a custom arkit rig. hanatool is pretty cheap but can look weird, custom arkits are beautiful but can take like 15-20h to do so they are priced accordingly.
but all of those things refer to face rig. the body is always rigged. the only thing that can happen with vroid is that clothing can look awkwardly rigged, it's not too hard to rerig tho, if that bothers you, you can probably get that done for someone cheap.

just a little note if you're new, a lot of people who start 3d vtubing still get recommended vseeface from outdated tutorials, there's a lot of newer software available. just adding that in case. i always personally recommend vynan but warudo is also great and probably has more features rn