1 gold = 1 beaker with no structures to improve it (LIb/Uni). How many beakers a tech cost is a function of many things, but the key is the level and the map size.
As a baseline IW on std map at Chief is 72 beakers with no contacts. Regent it is 144, Sid 360.
So regardless of how many it takes, you accumulate beakers each turn as long as you have research above zero or a scientist. So if you make 5 beakers this turn at 100% and have some in the box you get 5 beakers closer to the breakthrough. If you set it to 10% and get 4, you are missing out on one breaker.
The key is to note how many you get per setting of the slider. IOW if 10% to 90% all yield 4 beakers, it makes no sense to use 90%, but if 100 get 5, it could be useful to get that extra beaker.
One more per turn for 30 turns could spell being first, among other things. Once the breakthrough is going to be achieved, you will want to reduce the slider to save over runs, which are lost.
I once wrote an xls to track my beakers to know what my overrun would be and change the slider and maybe citzen to avoid waste. It turns out that other tools are vailable and much easier to use as they are passive, mine required me to input the projected beakers, tedious.
To sum it up, it can make a difference to use 100 vs 90 or some other setting from the very start, even when it is saying it is 50 turns at all levels.