Develop RK3399 and other related projects and products for evaluation. Recently, I found that Rock Pi4 is a good evaluation version. The price is reasonable and can meet the evaluation development. Just like the Raspberry Pi, the pin interface is reserved. It is a good fast landing arm. One of the better options for a range of products and projects.
Zero: Based on Amlogic S9-5Y2
   The SoC used in the Radxa Zero is the Amlogic S905Y2. The main system CPU is a quad-core ARM Cortex-A53 CPU with unified L2 cache to improve system performance. Additionally, the Cortex-A53 CPU includes a NEON SIMD co-processor for increased software media processing capabilities. The graphics subsystem consists of two graphics engines and a flexible video/graphics output pipeline. The ARM G31 MP2 GPU supports OpenGL ES 3.2, Vulkan 1.0 and OpenCL 2.0, while the 2.5D graphics processor handles additional scaling, alpha, rotation and color space conversion operations.
  
ROCK 3: Based on Rising Micro RK3568
  ROCK3 is Radxa's SBC (Single Board Computer) series based on Rockchip RK3568. It can run android or some Linux distributions. ROCK3 comes in two models, A and B, with 2GB, 4GB, 8GB memory options for A and 4GB and 8GB for B.
ROCK3 features quad-core Cortex-A55 ARM processor, 32-bit 3200Mb/s LPDDR4, up to 4K@60 HDMI, MIPI DSI, MIPI CSI, 3.5mm jack with microphone, USB port, GbE LAN, PCIe 3.0, PCIe 2.0, 40-pin color expansion header, RTC. In addition, ROCK3 supports USB PD and QC power supply.
 
*ROCK Pi 4: Based on Rising Micro RK3399
Price range: 400~1000, different configurations have different prices, divided into emmc and no emmc.
The ROCK Pi 4 is Radxa's SBC (Single Board Computer) based on the Rockchip RK3399. It can run android or some Linux distributions. ROCK Pi 4 features a hexa-core ARM processor, 64-bit dual-channel 3200Mb/s LPDDR4, up to 4K@60 HDMI, MIPI DSI, MIPI CSI, 3.5mm mic jack, 802.11 ac WIFI, Bluetooth 5.0, USB port, GbE LAN, 40-pin color expansion header, RTC. In addition, ROCK Pi 4 supports USB PD and QC power supply. The ROCK Pi 4 comes in two models, Type A and Type B, each with 1GB, 2GB or 4GB memory options.

*ROCK Pi S: Based on Rising Micro RK3308
Price range: 100~200
ROCK Pi S is Radxa's SBC (Single Board Computer) based on Rockchip RK3308. Equipped with a 64-bit quad-core processor in a 1.7-inch size, USB, Ethernet, wireless connectivity and a voice detection engine, it is ideal for IoT and voice applications. The ROCK Pi S comes in two memory sizes, 256MB or 512MB DDR3, and uses a uSD card for the OS and storage. Optionally, the ROCK Pi S can be supplied in an onboard storage version with 1Gb/2Gb/4Gb/8Gb NAND flash.

ROCK Pi E: Based on X86 chip
The ROCK Pi X is Radxa's first X86 SBC (Single Board Computer). It can run Windows and Linux distributions. The ROCK Pi X was launched after the Radxa team received a large number of users asking if the ROCK Pi 4 could run Windows. ROCK Pi X with Intel Cherry Trail Quad Core Processor Z8350, 64-bit Dual Channel 1866Mb/s LPDDR3, Up to 4K@30 HDMI, 3.5mm Jack with Mic, 802.11 ac WIFI, Bluetooth 4.2, USB Port, GbE LAN, 40 Pin Color Extended Header, RTC. In addition, ROCK Pi X supports USB PD and QC power supply. ROCK Pi X comes in two models, Type A and Type B, each with 1GB, 2GB or 4GB memory options. For detailed differences between Type A and Type B, please see Specifications.

ROCK Pi N10: Based on Rising Micro RK3399Pro
The price range is: around 1000~2500, and the prices are different for different channels and configurations.
ROCK Pi N10 is Radxa's SBC (Single Board Computer) based on Rockchip RK3399pro.

Summarize
Through the above comparison, combined with the current mainstream RK and RV localization bias, ROCK Pi 4 (based on RK3399) and ROCK Pi S (based on RK3308) are recommended for IoT, which can save uboot, kernel, and rootfs. Let the customer only care about the application, of course, if new devices are added, the driver is still an inevitable part.
However, rock pi saves us some stability-related issues such as uboot, kernel, rootfs, etc., which can allow us to use this series of product solutions quickly.