I've run custom roms in the past, when Cyanogenmod was the rage, on an HTC Desire (bravo). The main reason was the 576mb of ram made increasingly bloated Google services untenable. I think I modded another HTC after that, but then went down the rabbit hole of the Iphone 5. After that one got tiresome/wore out, I turned to Xiaomi, which was reasonable hardware and a great price. This includes:
Xiaomi Redmi 4A (a slim device, but underpowered with 2gb of RAM and 16gb of storage, and non-HD screen)
Xiaomi Mi A1 (a bit heavy, good screen, overall nice specs, comes with Android Experience which has significant problems with wifi/bluetooth speeds)
While the Xiaomi Mi Pad 4 ships with Google Play installed, if one does a factory reset, then the resulting MIUI 9.x does not bundle with Google Play Store or the GBoard keyboard. There are several steps needed to get it set up, including:
Find, download, install Google Play Store + Google Play Services
Install and enable the Google Gboard, and Gboard Keyboards
The Xiaomi Redmi 4A (aka Rolex) is a cheap (~100 USD) and lightweight (131.5g) 5" phone. For price, weight, and size, there is not much competiton. The screen is a 720 x 1280 px 16x9 screen that is pretty decent. Its got a Snapdragon 425 and 2gb of RAM with 16 or 32 gb of storage, and supports dual sim or single sim + microsd card.
On the negative side, the camera is weak, it is slow to open, and of course stock MIUI is slow and bloated, along with an annoying reminder to register your sim aka spyware on the prowl.
That said, there is nothing in a 5" screen that is as light and as cheap, and that means very strong value.