Especially if you're using any of Animator's interactivity features, it's worth thinking about what you're building as "software" rather than a design. I.e. even though the interface feels like a design tool, what you're creating is a production UI.
As part of that mindset, there's really no silver bullet for what limits to respect, etc. — just as you can write non-performant code in Swift, you can create a non-performant UI animation in Animator. The best way to figure it out is to iterate, get it on a device, and iterate again.
Re: iOS specifically, have you tried out the Lottie export functionality? You'll find that it's generally more performant on iOS & Android because it uses native-based renderers instead of web renderers. Just note that Lottie doesn't support any interactions, and there are a handful of other features that won't translate 100%. It all comes back to iteration & experimentation.
Finally, if what you're delivering is a prototype or explanation aid instead of slated-for-production UI, you may find some success in exporting an mp4, which should render performantly on just about any device.