Hardware Configuration for a Production Tile Server with high usage and serving multiple styles?

This is a community help forum. What you seem to be after is not general help, but specific consulting to help you achieve your goals in a specific commercial project. Consider getting commercial advice.

Generally, the server performance has two aspects: How quickly new tiles can be rendered, and how quickly existing tiles can be served from the cache. A tertiary aspect is how quickly you will be able to apply updates.

Rendering speed depends mostly on how fast your database disks are and how well engineered the style is. You cannot work without SSDs, and for a high end server you should consult with your vendor about what setup gives you the lowest latency and fastest random I/O access. A standard server with 64 GB RAM, 4 quad-core CPUs and fast SSDs with the standard OSM Carto style will give you a rendering performance in the general range of 1-5 metatiles per second (64-320 tiles per second). On lower zoom levels this performance will be much worse, and it is not unheard of for certain metatiles on z6 or z7 to take 120 seconds and longer to render, even if fast disks are available.

Tile access speed depends on the speed of the disks that hold your cache. Massive random I/O is not so important here so it is normally ok to use standard disks. Network I/O can become an issue. Your requirements are massive. 30k tiles "at once", let's say within the same 5 second interval, means 6k tiles per second, with an average tile size of 10kb that's 60 MB per second read from disk and a 500 mBit/s link saturated.

You might get to a point here where it could make sense to have one or more caches in front of your tile server, so that the caches, which would be easily scalable, could take the brunt of the high load. But this depends heavily on your usage scenario, and whether people are likely to request the same tiles often.

You will roughly need about 1TB of SSD space for the DB, 300 GB of tile cache per style, 64 GB RAM, 8 CPUs. Boot drive size is really not an issue.