Hello @hansmaulwurf Welcome to the community. As per my knowledge If you are deciding between the Raspberry Pi 4 and the Raspberry Pi 5

Here are a few points to consider
Performance
Availability
Budget and Requirements

If you need a Raspberry Pi immediately or have a timesensitive project; the Raspberry Pi 4 is a great choice. if you can wait and want the latest features, the Raspberry Pi 5 is worth it. It offers better performance

4GB and especially 8Gb seems like overkill. Has anything on Recalbox EVER needed that kind of Ram? Highest i'd go on a Pi would be 4GB. 8GB and up should be reserved for the Next generation.

@Dom

the only thing to do with the HD 3,5 inch tft screen is to add this config in config.txt file

#3.5 HD tft screen 800x480
dtoverlay=dpi24
overscan_left=0
overscan_right=0
overscan_top=0
overscan_bottom=0
#Banggood
framebuffer_width=800
framebuffer_height=480
dtparam=spi=off
dtparam=i2c_arm=off
enable_dpi_lcd=1
display_default_lcd=1
dpi_output_format=0x6f015
dpi_group=2
dpi_mode=87
hdmi_timings=480 0 16 16 24 800 0 4 2 2 0 0 0 60 0 32000000 6
display_rotate=3

and all is done. I'm going to write documentation about these screen