Rockchip RK3399 motherboard

Introduction:
This system uses an RK3399 as the main control chip (available on Xianyu for around 40 RMB each), with two 2GB LPDDR3 memory chips (18 RMB each * 2), a 32GB eMMC, no Bluetooth, and uses the bare-bones RTL8188 for Wi-Fi. Common USB, HDMI, and headphone audio ports are routed from the HDMI port, and GPIO pins were not included. It is barely compatible with Orange Pi 4 LTS; the schematic is directly copied from the Orange Pi 4 LTS, but the LPDDR4 has been replaced with LPDDR3, allowing for the programming of Orange Pi systems. The impedance remains the same. The reason for
choosing JLCPCB's 3313 is that graduation is approaching, and everyone is preparing for their graduation project, which is a smart car based on domestically produced chips. A pure MCU solution is meaningless. Originally, I planned to use Allwinner's H5 or H6 directly, but due to the boredom during the teaching competition, I couldn't get the H6 paired with the RK1808 computing stick working, and I hadn't found a solution from Rockchip for the open-source platform, so I designed this RK3399 motherboard instead. In a sense, a graduation project might not need to design a six-layer board, especially since the RK3399 was a high-end chip at the time, requiring six- or eight-layer board layouts, compared to the H3/H5/H6 and RK3328 DDR demos which only had four-layer boards. However, I might still want to continue learning Linux and ARM boards, and later perhaps work with Alibaba's RISC-V chips? But after graduation, I'll have to follow the job requirements, and I won't have as much time as in the lab. After soldering the H6 in early November, I was thinking about whether to design a 3399 or a 3588 next, but after reading the design guidelines, the 3588 might require at least an eight-layer board with an inner copper thickness of 1oz. Even with a -400 coupon, the prototyping fee could be 600?