So after testing with Steam's FPS counter. With Cum Gen = True, Keep Cum = True, and loading up Fleack Position Bundle 2.2 Girlfriend preset.
Version 10.2.153 on start up has around 22 FPS, and with a ton of spit cum frame rates drops down to about 18 FPS on average, even with like 6 loads of cum it only lows about 16 FPS, clearing spit and cum goes back up to about 20 FPS.
Version 10.3.183 (undertow recommended one) on startup has around 18 FPS, and with just a lot of spit frame rates drops down to about 14 FPS on average, and once you cum 2-3 times about 12 FPS, though if you cum like 7 times it will drop down to like 11 FPS, and if you clear the spit and cum it only goes back up to about 16 FPS.
Version 18 on start up has around 16 FPS, and with just a lot of spit frame rates drops down to about 8 FPS on average, and once you cum 2 times lows about 3 FPS, and if you clear the spit cum it only goes back up to about 7 FPS.
Version 23 on start up has around 18 FPS, and with just a lot of spit frame rates drops down to about 12 FPS on average, and once you cum 2-3 times lows about 8 FPS, cum 3-5 times lows about 6 FPS, if you clear the spit and cum it goes back up to about 12.
Version 32 on start up has around 17 FPS, and with just a lot of spit frame rates drops down to about 10 FPS on average, and once you cum 2-3 times lows about 3 FPS, and if you clear the spit cum it only goes back up to about 7 FPS.
Version 34 (unofficial github version) on startup has around 16 FPS, and with just a lot of spit frame rates drops down to about 11 FPS on average, and once you cum 2-3 times about 7 FPS, though if you cum like 3-4 times it will drop down to like 5 FPS, and if you clear the spit and cum it only goes back up to about 11 FPS.
So yeah version 10.2.153 definitely the best one in terms of frame rate, but it is very CPU intensive where it was using all 8 threads of my CPU at 66%.
Version 10.3.183 is definitely the second best in terms of framerate, but probably the best one to use over all since it mainly only used 4 threads at around 35%, but stayed consistently high and smooth.
Version 23 and 34 are okayish to use while creating characters so that you can enable the local settings. But wouldn't recommend for actual playing.
Version 18 is by far the worst, and version 32 isn't that far behind. Wouldn't recommend using at all.