Is it basic to transfer from one to the other? And are their credits recognized within each other?
Unless there is a formal transfer agreement in place, no college is required to accept credit from any other college. Some will accept no transfer credit from anywhere (Princeton) while some will accept 100% of the degree requirements in transfer (Excelsior, Charter Oak State, Thomas Edison State). Most are in the middle there somewhere with 60 hours from community/technical college and 90 hours total transfer being the norm.
UNLV and CSU are both regionally accredited. For that reason, they should each have little difficulty transferring credit. They probably do not have the same degree requirements though. If you take music appreciation at UNLV as a core gen ed requirement course but CSU requires Art History in their core instead - that music appreciation course will transfer as an elective or not transfer at all.
That’s where you’ll need to be most careful in what you take before you try to transfer it. If you are certain you’re going to transfer from UNLV to CSU then it matters little what UNLV requires for their degree and only what CSU requires for theirs. Ideally you’ll want to take courses that are required by both.
You’ll also want to time your transfer so that it happens after 30 hours (admission requirements are easier after 30 hours if you have a good college GPA) and before 90 hours (after 90 hours you might as well finish where you are - you’re almost done).
The higher your GPA, the easier it is to transfer anywhere. The closer you can stay to 4.0 the more golden you will be.
Don’t expect a 100% transfer situation without a pre-existing agreement. If 100% acceptability is your objective then take all of your courses at CSU; they teach online these days.