That's a good job you've done on that bike. Is it the first bike you've worked on? The first bikes I worked on, when I was a teenager, didn't come out as good as that.
I would say you should always take the bike apart as far as possible, when painting it. As its a hassle keeping the bits you don't want to paint, out of the way.
As for it being a low end bike. Well its got a bit of style about it. It doesn't look like a builders truck has crashed in the road, and they've welded all the scaffolding poles together, as they lay in the street. As some bikes do. :/
Ive got a couple of bikes that are a bit higher quality than that.

A GT Interceptor. I got it from the scrap yard for a few pounds, did some work on it.

A Haro F2 BMX. Same as the GT, bought for a few pounds and done up. Probably cost me £10 a bike. I was thinking of selling them. Ive been looking on ebay, but think its a bit of a hassle to post a bike. And Gumtree or FB selling pages just bring dreamers that want to swap a mobile phone or something, for the bike.
So there are "better" bikes available, at a good price. Its just how to find them.

Alec