Hi hi! Well, for starters, I’ll say I’m pretty fortunate my current computer can handle it, because lord knows I have no self-control when it comes to downloading CC. :3 I spoke a little bit about my current computer specs here. I’ve had this computer since 2012 (although I did video card/power supply updates in 2013 and I installed the SSD last year). But before that, I was playing TS2 for yeeeeears on a crappy laptop I got from my university and an older desktop computer that took a solid hour to start up (I couldn’t even keep all expansion packs installed).
I have only played TS3 very briefly – I have a lot of reasons why I dislike it, but one huge factor is that in spite of my computer specs and how TS2 runs like a dream, TS3 was very laggy. The open worlds took forever to render. I had a handful of CC and maybe two expansion packs installed, and it took AGES to load. I really think a lot of it is due to the bloated nature of the game itself, and not necessarily your computer. Of course, everyone’s computer is a little different, but overall I think TS2 is a lot more forgiving in terms of how it handles a lot more CC. TS2 has its own flaws and glitches, but it’s generally more stable.
I’m currently hovering between 15-15.5 GB of CC, which (believe it or not) is the lowest I’ve had it in awhile. It takes about 20 minutes to get to the neighborhood screen, and about another 5 minutes to load CAS or a family for the first time. But I’m reeeeeeally working on trimming it down even more, mostly because I tend to use the same pieces of CC over and over again anyway and its pointless to have so much cluttering my catalogue. D:
TL;DR: TS2 rules and I don’t think you should let your negative experience with TS3 discourage you from trying it!