Does running both (XCode & Android Studio) at the same time overload my MacBook Air with only 8 GB of Ram This IDE is for the Automation Testing Purpose.

Along with Appium Server, I need to run the Emulator of Xcode's iOS Emulator and the Android Studio's Emulator. 

Does this Run smoothly in the 8GB RAM of Macbook Air.
Yes you can and should load up your machine and see how it behaves. I don't think you'll get an overload at all.
The activity monitor will tell you when you run into memory pressure and you can see if swap helps or if you have a workload that would save you time on different hardware.
I’ve still not replaced my 2015 MacBook with 256 NVMe SSD (blazingly fast storage when it was introduced and still in the ballpark on 2019 models for what I need)

I run mongodb, make single page web apps, design and test API and deployment scripts, package Mac software for enterprise distribution, sign apps, notarize apps and generally work / debug / program and develop on this machine. Yes, some newer hardware is faster on benchmarks but in real life, I'm the thing the computer is waiting on always in terms of getting meaningful work done and I know how to measure when I'm waiting for the computer and can then buy a different kit when (and only when) I know I'll save money or time with more horsepower or more RAM.
In fact, developing on this means my solutions run even faster since I know when I make a bad decision and memory isn't free and to make a better database query, better data structure, more elegant code rather than assuming everyone that runs my apps spent $4000 on their portable.