Overview:

Other affected mods:

adds many new recipes, most of which fall into 3 categories: compatibility (such as Alex's Caves ore crushing recipes), QoL (using Create recipes to more easily obtain certain Alex's Caves resources), and utility (using Create recipes to make certain Alex's Caves blocks/items renewable)
adds an optional resource pack with compatibility textures (like making Create's chocolate look like Alex's Caves chocolate)
adds a new recipe type that makes use of both mods' mechanics
fixes certain bugs when these mods are used together

renames Create's Limestone to Dolomite since Alex's Caves also has Limestone (if the optional resource pack is loaded).

adds Bulk Corroding recipe type, which works by placing Acid in front of an Encased Fan. Currently used to rust/oxidize all blocks that interact with Acid.

retextures and renames Alex's Caves' diving gear and the Copper Valve to make them more distinct from Create's (if the optional resource pack is loaded).

retextures Create chocolate to match Alex's Caves color palette (if the optional resource pack is loaded)
makes Create sweets appear in Candy Cavity chests, and Gingerbread Men will try to steal them

For a full list of features, check out the wiki