I came across a free ebook by Roger Carter on Smashwords about using an Android tablet as a computer (see My Tablet – My Computer). The book is short, running just over 5,000 words. While I do not personally need to use an Android (LineageOS in my case) tablet as a computer (not to mention my 2013 Google Nexus 7 might struggle in some areas), I was curious to see Mr. Carter’s set-up and recommendations. It provides a nice tutorial to setting up an Android tablet to behave like a computer (I was not aware of some of the settings he toggled) and is worth reading if you have a use case for this set-up. Regarding apps, I would personally opt for a different set-up from the perspective of preferring LineageOS (or other similar ROMs) and open source apps to the stock Android suite. For example, because I do most of my writing drafts in markdown, I would rely heavily on Markor as my text editor. But if I needed word processing, my first inclination would be to try the open source Collabora Office. For keeping everything in sync between my devices, I prefer to rely on Syncthing instead of a third-party cloud.
Rather than replace your old, slow computer with a new one, why not buy a Bluetooth keyboard and mouse for your Android tablet instead? This book explains how to set up your tablet to replace your computer, what apps to install, and how to configure your new system. It will not only handle all your home office tasks, it will be much faster and in many respects more capable than your old computer.