Is there a FM like Caja?
I did before and some resolutions were squashed (A line going across monster. Mate never did that with the generic or Nvidea driver.)
Any terminal like Mate Terminal, I like the look of that 1?
I found How to Install KDE on Manjaro Linux that seems like a good guide, but Change Desktop Environments on Linux - YouTube says you should install the distro .iso with the DE.
Dophin is the default file manager in KDE, but if you like Caja you can still use it in KDE as far as I know. Just to go the settings → default applications and set it as your file manager.
Regards,
Damian
As @damiank said.
The default terminals are Yakuake — which drops down from the top of the screen when pressing a hotkey (usually F12) — and Konsole, which acts as a standalone window.
Both are using the same terminal emulator in the background, and they can be customized, albeit that you need to create a new profile for that, as the default profile is read-only. It’s easy to do, however.
Information provided in the HowTos here at the forum is always going to be more reliable than any information on YouTube.
Exactly, I forgot to mention he could change terminal exactly the same way 
What is the link to a guide I should follow?
Here you go… 
sudo pacman -S plasma kio-extras
pacman -S kdebase
/usr/bin/cp -rf /etc/skel/.
Is all I need from How to Install KDE on Manjaro Linux right?
SDDM is already enabled, one big thing though, almost all resolutions were squashed (a line going across 1/3 the height of screen) midscreen, rest of screen was black when I first tried it. I only had the generic driver (Mate doesn’t Squash any resolutions with the generic driver though), weird, why?
If you have issues with the resolution one great tool is xrandr
It is a bug, the whole screen is squashed in the middle 1/3,<----> is fine. Windows & the Mate DE is fine. Just KDE does it. The top 1/3 & bottom of the screen is just black. Btw, that link is a good way to install it right, if I ever decide to?
I’ve been using Manjaro KDE (I’ve downloaded directly the ISO and installed), but it looks like that page has a lot of info on KDE and apps.
Will a .iso with 6 be available when it comes out?
I think it will
I do want to follow the link & install KDE, but Mate is working for me & I am abit worried about ruining my install. I love the global dark mode of KDE.
I think I have been following this now. And let me say this:
If you want to change, then change. There’s no better way to find out if you like something or not that actually actively using it. That’s how I made up my mind between KDE and Gnome.
If you’re unsure, try a Live environment. Just remember that while it is very much, extremely the same, it’s not identical. Due to difference in who changes and customizes things.
Bottom line:
Only you can decide if you like something. Only you experience things as you do. So go ahead, test it with a live environment. If you like it, if it works well, change and test it. If you sit around and compare it, you’ll never get around to using it and knowing. And there’s only one way to know something like this…
In terms of file managers you have a lot to choose from. You are not tied to the desktop manager’s default. KDE & Trinity (a lighter fork off KDE3) support several actually in just KDE. You can also run Caja, Nautilus, Krusader, etc as long as you have the libs for that framework installed. There are also a lot of generic X11 file managers out there.
Personally I like Krusader as it handles tabs I feel than any other, and dual window display is a default. What I like most is while you can do drag and drop, I’ve never been a fan of it. I don’t want to be asked do you want to copy, or move, and deal with the inevitable accidents, etc. I love the support for dir comparisons, and other utilities built in. Including quick easy shortcuts to ~ and /. The bookmarking makes more sense and being dual paned I’m not doing a bunch of clicks. I select my files, then select the button to do what I want. Delete, move, copy, etc. I also really like the customization on the fields. Extensions mean a great deal to me. So sorting by extension which so many file managers lack by default or sometimes at all is a big plus for me with Krusader.
Anyway as long as you have the supporting libs you can run almost anything on almost any desktop manager. I personally use a mishmash of KDE, Gnome, X11 mostly. Best of breed app for what I want to do. So I’ll use Kid3 QT for tagging, then use Gimp for complex image editing. I might use Eye of Gnome or Gwenview for viewing a dir of images depending on what I want to do, but have Kphoto set up as default for most image formats so I can take a quick look at an image without loading the whole kit and kaboodle.
That’s the point of Linux. Do it your way. So I suggest exploring, finding the apps you like most.