TL;DR: The small H2+/H3 boards unlike their bigger siblings are all prone to overheating due to smaller PCB size (on the larger boards the PCB's groundplane acts somewhat as a large heatsink dissipating heat away from the SoC). Due to mainline kernel settings not being optimized currently all these boards are slower under constant load compared to legacy kernel. This should change but won't unless someone is looking into it and spends some time on this.   Two areas that deal with this