I'm planning a fairly large WooCommerce store—about 50,000 products, filters, search, inventory import/update, and roughly 10,000–15,000 visitors per day.

I'm currently looking at hostpro.com and trying to figure out which configuration to start with.

My requirements: NVMe, 8–16 GB RAM, 4–6 CPU cores, daily backups, and 24/7 support.

What else would you install on a server like this—Redis, OPcache, a separate database? And does it make sense to go with 16 GB of RAM right away?

Package plans from justvps.pro and planethoster.com can be quite right for you.
They are the fastest web hosts,easy to use, user friendly, mail upgradable, got everything from the homepage, single click everything you got, mails are faster when sent or received, attachment so easy, no expertise required to use it.

The backup implementation at HostPro is more useful than a simple snapshot system in my opinion. VPS servers are backed up remotely on a daily basis, with copies retained for up to 30 days, and restoration can be performed for the entire server or individual files and directories. That gives administrators more options when recovering from configuration mistakes or accidental deletion.