Disable all desktop effects, that should make it respond much faster. I’m also running Mint 19 Cinnamon on a 10-year old laptop with an i3 and 4 GB of RAM. It runs just fine after disabling all desktop effects.
The effects are cool in the beginning, but get old after a while anyway…
Yesterday I updated the install script for Rapid Photo Downloader so it works on CentOS 7.5. It was my first time to try CentOS. I was very impressed with its stability. Everything “just worked”, in a VirtualBox instance at least (I wouldn’t want to run it on bleeding edge hardware though). The interface is very bare bones.
My impression is that running the most recent Fedora core is pretty much exactly like running a development version of Ubuntu. Things break from time to time.
Cheers for that tip. Out of interest (and derailing this thread further!) I’ve installed XFCE onto my mint 19 mate install. And disabled all desktop effects. Pretty zippy now. So do I stick with my Mint 19 Mate with XFCE installed, or go for a clean install if Mint 19 XFCE? Possibly something to experiment with!
I thinknMint will give you their “xapps” suite regardless of which desktop environment you have.
Settled with Mint Mate 19 now. Reinstalled / refreshed the Firefox plugins as that seemed to be causing the slowdown 
Now I’ve chucked all my other distro dvds in the bin 
Glad you are settling. I had a phase when I changed my OS almost every week. It was like an addiction and lasted several years! 
Now Mint 19 Xfce.
Nice and light and fast!
What did you end up with?
It is no secret that I use Windows 10, from many of my posts and this poll, and I am always grumbling about it. People here ask me WHY? Generally, I use apps that can’t be run on a compatibility layer and dual booting is a pain. If I were to use Linux, it would be in a virtual machine; however, it would be clunky and annoying to maintain, esp. with a system as limited (processor, RAM and storage) as mine.
PS I do have a few VMs hanging out in my spare disconnected disks. If I were to run one today, it would be Linux Mint Xfce. I also install and maintain Linux Mint on my parents’ and friends’ computers. I find that it is sensible for beginners. I used to use Ubuntu most often but I could not appreciate the desktop redesign among other changes.
I used to be obsessed trying new distros and the super lightweight ones especially. Now I just want something that looks nice and “just works”. Pop OS is my daily OS on my laptop. Latest Ubuntu but with extra tools and polish on top.
Kubuntu 19.10 installed today!
And replaced today with good old Linux Mint Cinnamon Edition! 
LOL well I actually have Fedora on the SSD now. For how long?
Distro-hopping within Ubuntu(-based) distros? Aren’t they more similar than different? I have Fedora since 1 day now and I know that it won’t stay long: Nvidia Prime works, Intel Neo works too, but there is no sound when using tiling window managers. I have googled carefully for a solution and I am really bored by Debian, so I was actually ready to stay with Fedora, at least for a while.
lol, I’m still not happy with Mint Cinnamon. As you say, @betazoid Ubuntu-based distros are more similar than different.
So I think I’m going to go with Manjaro. A bit more care required with updates, but at least it’ll be an easy way to get up to date versions of photo editing software, without relying on PPAs. 
I have done partition images of my Mint install though, just in case!
Lol.
Manjaro KDE installed yesterday. Straightforward installation. Darktable etc 3.0.0 installed using pacman.
Big fly on the ointment is continual heavy disk access. Is it due to KDE? Manjaro?
Hmmm so what to do know… Spend days / weeks trying to diagnose the issue? Or try a different distro? 
Brian - do you have SSDs or what?
Amount of RAM?
Have you set up a swap partition? Size of it?
Check the swappability setting.
Have fun!
Claes in Lund, Sweden
Actually I have no problems of this kind with Manjaro. Everything works. It’s just that I don’t like the artwork, themes, backgrounds etc.
I suppose you have googled the issue.
Well I just solved the Fedora sound problem. I think I’ll stay with Fedora for now. Maybe you can give Fedora a try as well?
Since you have KDE, the process manager (ksysguard) can display the I/O rates of the processes. On a new install it is possible that this is the file indexing at work, and it may cool off after a while.