It’s largely a matter of personal preference. I have Signal and Keybase in their own templates, with each template having a single AppVM based on it. For Zoom, I use a StandaloneVM. Both are valid and supported choices, and both have similar security properties.
A TemplateVM becomes a big win if one has more than one AppVM based on it. If there is only one, the benefits are significantly reduced. The main exception is that if the TemplateVM’s configuration is easy to regenerate, one may be able to get away without backing it up, reducing backup size.