Can be a silly question. If i use multiple cam mod like uni can, gcam ect along with the stock cam app will it cause any damage to my device?...Hardware related or software related?
On the hardware side, definitely not. You will still be able to rotate the cam with the floating menu on the bottom right. On the software side, I'm no Asus engineer but I don't see how it could cause any damage. The camera experience is bug-free for me.
My experience on my Xiaomi phones with several Gcam apps at the same time and Open Camera is that these different apps do not interfere with each other at all.
Gcam apps can have various problems, like memory leaks - the amount of free memory can be reduced enought that they stop working reliably. A simple reboot solves that.
Also HDR+ processing (Gcam) is very computation heavy, can heat up the soc.
My Xiaomi Mix1 can get so hot after say 40 minutes of continuous closeup photography that I have to turn it off for a while to cool down.
My Z6 E. 30 does not seem to have any of these problems so far, no unreasonable heating, perhaps the 12GB helps.
Though I have read that doing video at 4K can heat it up after a while, haven't tried that yet.
So no, there should be no problems using various camera apps, just pay attention to how hot it gets..