Unsure about Umami's performance, but Piwik was a non-starter for several higher traffic sites I worked with due to performance issues (even after throwing big hardware at it).
Out of the similar alternative, I think Plausible is currently leading in scaling and performance.
I think this is also the reason why they are the most affordable in pricing.
Note: Not affiliate with them, just observation from researching GA alternatives.
One big difference is that Matomo doesn’t support PostgreSQL and has said they don’t plan to.