I'm not sure if anyone has tried before.
If can get rebate, yes, RM 50 is the max even if you spend more than RM 1k.
Both have its pros and cons.
I'll list out for VOX since this is UOB thread.
Pros:
i) VOX gives RM 50 cash back if you spend RM 1000 in a month while CIMB CR gives RM 30 only the remaining RM 20 is for other retails spending.
ii) VOX can be used to purchase flight tickets and get cash rebate while CIMB CR cannot give you any cash rebate.
iii) VOX is said to give 5% cash rebate for TM (UniFi and Streamyx) while CIMB CR can't, but this is yet to be confirmed as it will only appear on 30th Sept, I'll confirm later. KIV for this.
Cons:
i) VOX needs to spend at least RM 50 per online transaction to be eligible for cash back while CIMB CR has no such restriction.
ii) VOX has monthly charge of RM 6 per month if you didn't spend anything on it while CIMB CR is a free for life card.
So, you have to know your spending first.

For me, VOX has the advantage for me.
if unifi accepted for vox, then the monthly rm6 fee is negligible.
I'm same boat with u, desperately looking alternative card for unifi n tnb.