What LeonarX said. As someone that's used Chunky a lot, the main resource drain is RAM (random access memory), which computers nowadays usually have 8GB of by default (though you can't assign all 8 without your PC freezing). 4GB assigned should be enough for anything up to 2K x 2K blocks for sure, possibly up to 4K x 4K.

RAM determines how big of a map you can render, while your CPU decides how fast the render goes.

Most important tip, under 'advanced' settings, there's a 'Octree implementation' setting. Make sure that is set to anything other than 'Node'. That one 'setting' is acknowledged by the devs as being extremely slow, and I think it's mostly there for legacy reasons.

Thanks! It's a 3rd party application called Chunky. It's a bit of a curve to get used to and it's pretty resource intense, however with a bit of practice something like this isn't hard at all to get.