My advice is to keep both operating systems. Windows is useful.
Dual booting managed by Ubuntu works fine outside of corner cases with old hardware, and Ubuntu requires significantly less disk space than Windows. I've found 60GB is often enough for a primary and a swap partition in normal circumstances...not storing lots of audio/video/image data.
Another alternative is to buy a small SSD and swap it for the existing SSD/HD holding Windows. Then you can always turn the laptop back into a Windows laptop. I put the old drives in the box for the new drive with a piece of paper listing the Windows Activation Key and the administrative password to the installation...learned from experience.
Don't bet on 18.10 having better performance with your HP. I have a Dell Precision that Dell offered with Linux as an option and is actively supporting. I've had to learn to configure the touchpad with Xinput even though Dell was working on it. The underlying driver has changed four times over the last two years. Each time it does, I have to tweak Xinput (Now, I add commands to ~/.bashrc).
But why not 18.10?
+ Because you'll be upgrading in April 2019, October 2019, and April 2020. The last will be to 20.04LTS. In between, Ubuntu will be testing out alternatives that may or may not go into 20.04LTS.
+ And, things like trackpad and power management get backported to LTS. Those four changes to my Dell trackpad were all while using 16.04LTS.
+ In short, non-LTS releases like 18.10 are not about bug-fixing and LTS releases get bug fixes. That's what "LTS" means.
The reason to run a non-LTS release is if there is an application that requires it. Or for bragging rights. But mostly, non-LTS releases are more work...the first time the trackpad issue on my Dell came up, I discovered there was a fix upstream in September. So I installed Ubuntu 16.10 figuring it would be there. It wasn't. Around March 2017, it showed up in a 16.04 LTS update.