I'm currently looking to get a Ti Nspire CX to run programs on, Mainly Ndless stuff. I've heard that the CR4 model has suffered slowdowns compared to the CR3 model due to Ti changing some things about the LCD. Which would be the better version for me?

Yes, TI changed the screen they used back in 2015. There isn't really an impact in day-to-day use, but the asm and c/c++ programs that were already written by then (such as nDoom) stopped working because the buffer was now rotated 90° and mirrored. Newer programs that are compatible with both revisions will run slower due to the fact that they have to write to the screen buffer twice to account for the rotation and mirroring. If you're gonna get a TI-Nspire CX or a TI-Nspire CX CAS, you should definitely look at ones made before November 2015 (hardware revisions A-V). If you're looking to purcahse a new calculator though, it might be worth it to look into the TI-Nspire CX II [CAS], which is more or less the same price, but with a faster processor. I have also heard that ndless is more stable on older revisions, but that might just be some rumor going around, I personally haven't experienced it.

Alright, I will try to opt for a CR3 or older model. Thank you