There's many ways to play but you seem to have the gist of it. The big thing is really which version of the game you're playing and how ship speed works in that version.
For example in DL ship speed and more importantly the size of engine components means that you can at some level of tech get ships that can go large distances within only a few turns.
In DA the size (and cost) of engine components have been greatly increased and the speed (a misnomer actually the distance you can travel in a single turn) has been reduced so much that it can take quite a few turns to go from one end of a map to the other.
Many folks have argued that there should be at least some function of map size in ship speed but that has never happened.
As far as TA is concerned I think the nerfing of speed that occured in DA was relaxed somewhat but not quite back to the levels of DL, however I can't be sure as I've never yet played TA.
But there is not contribution of map size or number or frequency of planets to tech cost so clearly as you get more planets you can run through the techs more rapidly because of having a higher level of reseach than with fewer planets.
And I personally use the largest maps possible but then I might take 6-8 weeks to finish a game.