you can change recalbox menu resolution between few modes
You just have to edit recalbox.conf file, this line below only.

;system.es.videomode=CEA 4 HDMI

it will be (for exemple)

system.es.videomode=CEA 2 HDMI

You have to delete " ; " on the begening of this line also
and
You can change " 4 " by an other value (2 for exemple), take care to not use so high resolution on RPI, or it will overheat and slowdown games (under 1080)

Value between 1 and 65
(65 is custom)

1 VGA (640x480) 60Hz 4:3 2 480p 60Hz 4:3 3 480p 60Hz 16:9 4 720p 60Hz 16:9 5 1080i 60Hz 16:9 6 480i 60Hz 4:3 7 480i 60Hz 16:9 8 240p 60Hz 4:3 9 240p 60Hz 16:9 10 480i 60Hz 4:3 pixel quadrupling 11 480i 60Hz 16:9 pixel quadrupling 12 240p 60Hz 4:3 pixel quadrupling 13 240p 60Hz 16:9 pixel quadrupling 14 480p 60Hz 4:3 pixel doubling 15 480p 60Hz 16:9 pixel doubling 16 1080p 60Hz 16:9 17 576p 50Hz 4:3 18 576p 50Hz 16:9 19 720p 50Hz 16:9 20 1080i 50Hz 16:9 21 576i 50Hz 4:3 22 576i 50Hz 16:9 23 288p 50Hz 4:3 24 288p 50Hz 16:9 25 576i 50Hz 4:3 pixel quadrupling 26 576i 50Hz 16:9 pixel quadrupling 27 288p 50Hz 4:3 pixel quadrupling 28 288p 50Hz 16:9 pixel quadrupling 29 576p 50Hz 4:3 pixel doubling 30 576p 50Hz 16:9 pixel doubling 31 1080p 50Hz 16:9 32 1080p 24Hz 16:9 33 1080p 25Hz 16:9 34 1080p 30Hz 16:9 35 480p 60Hz 4:3 pixel quadrupling 36 480p 60Hz 16:9 pixel quadrupling 37 576p 50Hz 4:3 pixel quadrupling 38 576p 50Hz 16:9 pixel quadrupling 39 1080i 50Hz 16:9 reduced blanking 40 1080i 100Hz 16:9 41 720p 100Hz 16:9 42 576p 100Hz 4:3 43 576p 100Hz 16:9 44 576i 100Hz 4:3 45 576i 100Hz 16:9 46 1080i 120Hz 16:9 47 720p 120Hz 16:9 48 480p 120Hz 4:3 49 480p 120Hz 16:9 50 480i 120Hz 4:3 51 480i 120Hz 16:9 52 576p 200Hz 4:3 53 576p 200Hz 16:9 54 576i 200Hz 4:3 55 576i 200Hz 16:9 56 480p 240Hz 4:3 57 480p 240Hz 16:9 58 480i 240Hz 4:3 59 480i 240Hz 16:9 60 720p 24Hz 16:9 61 720p 25Hz 16:9 62 720p 30Hz 16:9 63 1080p 120Hz 16:9 64 1080p 100Hz 16:9 65 Custom

https://github.com/recalbox/recalbox-os/wiki/Video-configuration-detailled-(EN)

https://www.raspberrypi.org/documentation/configuration/config-txt/video.md