The 2019 model Lenovo Flex 14 offers a decent amount of performance considering its USD $800 price tag. While it fails to stand out in any meaningful way, it is still an overall good bang-for-the-buck convertible.
https://www.notebookcheck.net/Lenovo-Flex-14-2019-Core-i5-8265U-Laptop-Review-An-average-convertible-at-a-good-price.426902.0.html
Crappy chinese copy of a crappy Dell 2-in-1 ;D
[Have owned this device for several years]
This 2 in 1 is a decent buy used, but beware that the battery will likely need to be changed. The swap is quite easy. While changing the battery, there is a single DIMM slot that can hold 16GB modules. Those are a cheap upgrade to memory capacity. The SSD is a standard size and easily replaceable. For less than $100, you can have this device running a 1TB SSD and 20GB ram.
Using a program like throttlestop, you can undervolt the processor to achieve better sustained performance. Also, upgrade the BIOS to the latest available from the manufacturer for security reasons.
We've gotten good service from this device. The hinges and case have held up well.