From what I've seen - and logically I've no reason to think it'd be different at Suicidal - its actually easier to win with more opponents to start with than fewer.
I agree. Also, as someone noted elsewhere, huge maps are easier 'cause they ask more for a long term strategical effort then a tactical one and the AI is, obviously, weaker at strategy.
Personally i play suicidal, huge maps, but very few inhabitable planets. My strategy is to rush for sensors and get all the possible bonuses (and money) from anomalies, while i go out for exploration with 4-5 cargo-scouts (which i will soon upgrade in survey vessels), a couple of colony ships and some constructors.
Like wyndstar i too always spend the 4 points for the 30% economy bonus but, because i play with tech trading on, as super ability i choose diplomacy.
About the ethics i go for neutral. All in all is the best choice.You can make very profitable (and long term) evil choices during the game balanced by the loss of few money coming from good choices.
If i have time, because of peaceful opponents around, i immediatly research for better forms of government to keep my economy in shape. If there are some dangerous races in the neighborhood i try a war at the end of my first or second year, as soon as i discover the medium hull technology.
I know that there is an endless discussion about defense but, in my experience, i always win my first war due to defense. I don't need to search the most powerful weapon, only the right one to strike my opponent. My ships last for a very long time and, while i upgrade them, i can build constructors to implement my starbases on resources or i can make money.
I use a lot of spies when i go to war. I don't know if they are a tactical turn in my favour but when i start a war i place about 7-10 spies on the planets of my opponent to stop his production and slow the research. I start to produce spies since the 1st turn of gameplay. Compared with the money you receive from tech trading and anomalies, the cost of spies in the very beginning is nothing.
Anyway the key, in my style of playing, is micro-management. I work with the bars almost every turn during the first year. Later, when i'm enough powerful, i can even ignore the bars (if i don't need to change radically my strategy) but, in the beginning the micro-management is everything. It's a lot of saved money and a lot of advantage on the AI (i.e. before exploring an anomaly, i change the tech i'm searching with a more expensive one, in case the anomaly will give me the 25% research bonus).
So, in my games anomalies and mining resources are more important than planets. At least in the beginning. This depends probably on the fact that i play with few inhabitable planets but, on the other side, the truth is that from anomalies and bonus resources i get so much bonuses that i always cover any gap with the AI. From this solid position i start my conquest. Obviously there are a lot of changes and correction in my strategy depending on the global situation and on the opportunities around, but in the end the galaxy is going to be ruled by only one power.