Originally posted by Syri:

The terrain modification issues were fixed before the hearth and home update. Altering terrain now should make no difference to performance. The only exception is if you're using any mods that do terrain modification, as some of those could still be using the old system.
I've raised land out of the sea, cut a harbour into a land area, flattened a large area to build a town and re-shaped the coastline on a fair sized island, without any issues.

Wrong, depending on your hardware it influences a lot. Fighting bosses at 60 fps here, my base on the other hand, 40 fps.