are there any good channels/resources which explain the basic elements of the pro game, such as spacing, defaults, and when/why to implement each tactic?
My best advice to you is to queue up a bunch of unrated, lock in Cypher or other info agents, and do nothing but look at the map and mentally take note of where each agent on the enemy team shows up on the map and what abilities are used--even if it means inting the match.
You'll eventually learn to do this subconsciously while playing normally