Linux

If you're new, you should go with Linux Mint. It works great, and provides sane GUIs and defaults for everything, unlike most other distros. For a newbie, it's the best decision. I've personally have had 5 people on Mint so far, who were originally unhappy that I formatted away their Windows partition when I told them that "I will fix it for ya" (when they came to me with their laptop because I'm a computer person), but they came to all love Mint. They said "why wasn't I using this before?".

I use Linux since 1998, and I still use Mint. Sure, I have other distros installed (Debian-Testing is my default on my desktop, many other distros on my various laptops), but Mint is the one I use the most. It just works. Just because I know how to fix something in the command line doesn't mean I want to spend time doing it, GUIs are just fine!

In fact, I'm able to easily deliver both the MacOS and the Windows look, to lure new users in with Mint, haha: https://mastodon.social/@eugenialoli/114653608461737248

Try each. One of the great things about Linux is how easy it is to just hop around. Spin up a ventoy USB with those and maybe even a few other ISOs. Then boot into each one and go through the process of finding a piece of software (krita, for instance) and running it. Do a doodle of a dog and run a few filters or something. Doing so will tell you which one you like, which one your computer likes, etc.

As you are a noob, avoid arch.

It maybe great for your self esteem telling people you are an arch user, but vanilla arch is not a simple distro. it takes a lot of work.

So, unless you have a lot of linux and terminal experience try something else.

If you want to play with an arch based distro there is manjaro.

I have manjaro installed on my old Lenovo T450 for years and it works great.

Alternatively give linux mint XFCE a try. I usually install this for people who are new users of linux.

or I have MX-linux installed on the Mrs laptop. she has the lenovo T470.

install guides:

https://linuxmint-installation-guide.readthedocs.io/en/latest/install.html

https://itsfoss.com/install-manjaro-linux/

https://www.debugpoint.com/install-mx-linux/

if you want to try vanilla arch

https://itsfoss.com/install-arch-linux/

I’m thinking of something customizable (Arch)

Most distributions are customizable. The reason why Arch has this reputation of being customizable is, because it comes barebones and you have to build your own distribution out of it, basically. That means you need to learn and understand Linux and how Arch works. With other distributions you can still customize them to lot of degrees, you just start with an already build and tested environment.

However, there is a new trend of so called "immutable" or sometimes also "atomic" distributions. These work a bit differently, where the system is protected and either updated as a whole or in a special way. So deep customization (depending on what you exactly want to do) can vary in those cases. An example of such a distribution would be SteamOS 3.

Then there is also the release model you choose: rolling release or LTS (also known as point release). Archlinux is in example such a rolling release, which means it gets updates and often has the newest software available. But this comes at a risk and often the user need to understand what is happening in case of a problem. Therefore I recommend a beginner to Linux a system that uses a point release system (or also known as LTS in example) instead. Ubuntu uses such a system, and many others. This means it gets security updates and little features over time, but not always the newest version of a software with the newest features. What you get instead is "stability" in the sense of not changing too much and being less risky as well.

If you are new to Linux and want an easy to use distribution that is much Arch, but a little bit easier with preconfigured environment, then I would look at EndeavourOS. But I really do not recommend an Archlinux system as your first distribution, if you want an easy to use system. There are lot of other choices to make too, like the GUI and so on. Looks like you already like KDE Plasma if you want Kubuntu in example. The question is, why are you looking for a different operating system than Kubuntu in example? Why don't you install Kubuntu. I ask, because the answer could help in finding the right one for you.

Anyone suggesting a rolling release distro to you is setting you up for failure, especially on a 2014 laptop that will absolutely not benefit from it.

Use Linux Mint. It's still Linux, you can still ~~break it~~ customize it as much as you want.

edit: Y'all are absolutely insane to downvote this when we are talking about a NEW linux user using a 11 year old laptop.

Linux Mint.

Kubuntu is a pretty solid choice. It has an up-to-date KDE, and it's surprisingly snappy and resource efficient.

Fedora

If you're new to arch, I think maybe go endeavouros. A new install has update scripts and whatnot, and EndeavourOS has good documentation. Going straight into arch involves a lot of reading the docs just to even get a desktop environment running. You probably want to start with the full package.

I'm using endeavoursOS gnome.

Kubuntu will get you familiar with package management, though it could well be managed through a desktop app so you may well barely touch the terminal. But you will discover that there's a fair bit of bloat - not in the windows sense - but apps that you may not necessarily need.

I would caution against Arch. I don't think it breaks as often as people suggest, but you may run into a problem like steam not loading when you want to play something with your friends. That gaming session is shot unless you can fix it on the fly. After a few years you will, but you need to balance those kinds of growing pains against doing something you want to do in the moment. Don't expect it to work the way you expect every time.

Fedora a great. Very intuitive.

The happy medium would be Fedora KDE

Install a fixed distribution like Ubuntu, Leap, Debian,... and enjoy Linux and read the wikis of the chosen distribution. Once you have gained experience, install a rolling distribution.

I don't think regular Arch is the best for new Linux users at all but their are a few Arch based distros with graphical installers.

I'd you are trfh savvy, the Arch install process should be ok though.

Of the 2 you suggested, u would go with Kubuntu. KDE is a very popular desktop environment and Ubuntu is solid. I've moved distros quite a bit but always go back to Ubuntu-based. I've been on Mint for the last 6 or so years.