Looks like with some dead basic optimisations (free versions of WP Fastest Cache and Autoptimise), my Wordpress site can handle around 1500 requests per second on a $5 DigitalOcean VPS before it starts to slow down.
On the old site, running on a shared host with less optimisations it would crap out at less than 10!
Seems like I don't need to worry about this after all.