How reliable are the Roblox Studio Animations?

I have been making an fps and my animations seem to be the biggest problem because they take the longest to design and they sometimes don't do what I want them to do. I have two methods of animating. The first one is a custom weld system where I lerp the arms to a specific point and can cancel at any moment. The second one is an animation system where I animate a rig on blender, export it, and then put it into a rig on studio and hope it works(if you can't tell, I am not entirely familiar with this method and don't know if it will 100% work). My two questions are, will this exporting work from blender(the system just seems iffy) and how reliable are the "Animations" in the studio. In other words, will they play 100% of the time or sometimes just not work, ending up in an unfinished animation or the arms not showing up? Any answer helps!