I think Google is capable of handling SPAs these days (it can execute js now), so works fine mostly (might still be better to serve full HTMLs to start with).
It technically can render javascript, but there's a performance penalty that negatively affects your crawl budget.
If you're twitter or facebook, or have enough domain reputation already that your crawl budget is big enough to offset, then it doesn't matter. If you are not already a big deal, then it takes a lot of off-site traction to overcome.
Practically speaking, for two otherwise-even sites just starting out, a statically rendered site has a pretty significant SEO advantage over a JS-only site.
If you're twitter or facebook, or have enough domain reputation already that your crawl budget is big enough to offset, then it doesn't matter. If you are not already a big deal, then it takes a lot of off-site traction to overcome.
Practically speaking, for two otherwise-even sites just starting out, a statically rendered site has a pretty significant SEO advantage over a JS-only site.