Yeah, like the OP I usually look around for a starting world within a "bag" that has one or two entrances, so that I can have a set of core worlds defended by solid chokepoints. As for starting ships, I'm pretty flexible, but I tend to pick either ones that effectively increase my triangle ship cap (Zenith Electric Bombers, Bulletproof Fighters, etc) or things that are fast and can be used as interceptors (Teleport Battle Stations, Raptors).
Ultimately, it doesn't matter too much what starting world you pick, as you can "create" choke points by destroying warp gates and guard posts on worlds from which you don't want AI dudes to show up, then post some token defenses there just in case a couple of AI guys come through anyway. That being said, I avoid starting on a world with more than two or three wormholes, as it's just too much of a pain to defend.