Reply to Debating Whether to Upgrade to CDJs in the Future

I have a Pioneer DDJ-Wego and I'm currently stuck in a situation where I can only use that for gigs. It's crapped out on me twice, and I'm expecting it to do the same this weekend. However, someone on reddit recommended me upgrading to some Pioneer CDJ-850s whereas my original plan was to always get a DDJ-SX.

I'm confused on how storing cue points work on CDJs. Are they stored on the Rekordbox USB? The CDJ itself? Do I need to buy SD cards in order to use them at all? Also how does hooking up DJ software work with those? I know the most recent Pioneer mixer was made with Serato involved, but does that mean Serato is a better fit for modular set ups? Could I use them with Traktor?

Biggest thing that's holding me back is the cost and lack of knowledge on good cheap mixers or alternatives for the mixer and CDJs as even refurbished and used Pioneer gear is pricey as hell for someone in college.

Ultimately, I plan to evolve my setup to include the use of Ableton to utilize lighting and visuals. Can I still sync up Traktor with Ableton if I use a modular setup?

Basically, tell me anything and everything about CDJs and whether or not it's a good/bad idea to switch today.