I am playing on Immense. I passed over the first few maps--I am always checking the tiles on the homeworld and the strategic layout of the stars on large maps, since I will be investing so very many hours playing on them. This is my first Immense and I love it. Yes, huge areas are void, but that adds to the challenge, since I am pretty clever about getting across them to check out the star clusters on the far side. Ship range and speed are important, as are sensor range and using constructors to make starbases to extend range. Often I send a constructor or two, a colony ship or two, and a scout or survey ship or two off across a long void. I will make a starbase when I reach the end of my ships' range, then push on to explore the closer stars searching for habitable planets.
Immense maps are not for the faint-hearted or casual player, IMO. I am using Tight Clusters, stars are occasional, planets are abundant (or common?). By about turn 120 I have made first contact with 3 other races, and expect to connect with the fourth very soon. The last race must be on the other side of the map and while I have ships headed that way, it will still be a while.
I like the ideology buff from Practical that protects you from others declaring war on you for 100 turns (is that one Neutral?). I did not use it until turn 90, so now I have time to explore and expand while two other races are in a arms race, building large fleets of warships. Since I have Extreme Colonization and they do not, I am picking up the Aquatic, Barren, and Frozen worlds near them as well as some fine standard worlds in the star clusters well away from their home sectors. On Immense, distance really dominates the strategic situation. Tight clusters keeps the number of stars to something that is not so overwhelming. In about another 30 turns I will switch to building up my fleets to match or exceed my neighbors by the time the 100 turns of peace are up. No doubt when it is the YOR will attack! I think the Drengin are too far away to be a threat anytime soon.