If you are doing things like running steps of commands from a web page, paste what you need and close the tab/window to save memory.

Check out Midori and Dillo for slim gui browsers, and links2/elinks/lynx or w3m for a fairly user friendly terminal web browser. I'm really bad about browsers on my laptops, especially when i'm researching something, so I have to be careful on a pi to not use too many tabs or browser instances. LXDE also runs well and is fairly user friendly. I do like the default window manager configuration with parrot better than kali, where I usually find myself installing xfce or i3. Both distros have pretty much the same standard set of tools, and debian style package management for upgrades and additions.

I haven't used parrot since somewhere in 2.x, and it was on x86. Some tools will just be too resource heavy to work well at all under a load, cough burpsuite. In my opinion they're both a little bloated for the pi, but you can speed them up substantially with a different window manager and/or web browser.

Parrot os raspberry pi