If the number of turns in the game is kept constant and the "number of turns" it takes to train a unit is kept constant, you'll have the same number of units late game either way. They may be different units, but the numbers will be the same.
Anyway, it is that simple. Currently, tech progress is limited by losing overflow. If you add in overflow but increase tech costs by the average amount of overflow, then tech progress continues at the same pace for the non-micromanager.
The point of adding overflow is not to make tech progress either slower or faster (those are separate issues and since I've seen arguments for both they're probably issues best left to mods) but to make it so you don't get penalized for researching techs in an order with lots of overflow. As it is, you have to make sure you research the cheaper techs early lest they mean wasting a lot of overflow later on and you have to multiply science per turn by turns to make sure you don't research a tech that's going to waste a turn on one or two extra beakers. With overflow, you research what you want because you want it. Without overflow, you either have to do a stupid spreadsheet exercise every few turns or cope with a ton of wasted resources.