Blimey, are Mesh still doing? The mini-tower next to me knee is a Mesh, it’s at least 15 years old and probably nearer 20 though I think the only original component is the case.
The only compelling reason I can think of to build your own these days is if you’re an enthusiast / gamer and want to specify every individual component. If something goes wrong with the build it can be a pain as there’s far too many variables to trivially troubleshoot.
Go with an established name, Lenovo / Dell / HP / etc. You’d be hard pressed to find something that isn’t up to the job of “browsing and streaming,” even second hand. Get something with an SSD.
What’s up with the existing PC? Anything that an SSD and a clean install of W10 wouldn’t fix?