I've seen some people argue in other posts that it's strange to have all the starting AI empires discover FTL travel all at the same time. If you set the number of AI empires to 0, then it would, in effect, make you the first species to discover FTL with several other pre-FTL species out there at varying levels of technology. This would be a more realistic progression, as different civs would achieve FTL over the course of the game and not all at once, but it would of course make the player very OP compared to the rest of the empires in the game. You could also have a couple of FE thrown in to simulate that you are not, in fact, the first race to achieve FTL, although you would still have a sizeable advantage over anybody who is not a FE.
I'm curious how pre-FLT species are generated. Is there a set number based on the size of the galaxy? Does every uninhabited system have a percent chance to have one? How many actual FTL empires are likely to develop over the course of say the first 50 years, if the player picks 0 starting AI empires? Or is it simply too random to even guess?
Also, it's possible that the late game events may make you wish you had several other friendly (or even not so friendly) empires at similar levels to your own to ally with.
I personally want to have some space around me so that I can explore a lot but I do want other empires out there to challenge me mid game as well. I plan on 1000 stars and 20 AI empires and I'll adjust it if that is too few or too many.