You shouldnt set static on any device end as its can cause issues with DHCP. Static ips should be controlled from the router end using fixed ip address or DHCP reservations. Same goes for DNS as well.
There is probably a config file in ropieee that you can set it in but updates at some stage might override it. @spockfish Harry would be best to advise on manually editing and which file location to use
If it’s outside the DHCP range it won’t mess it up though you are correct. But best practice is to let router manage this side of things thats what its for it as can lead to issues if you change network gear and it uses different ranges by default and can’t change the range it uses which has caught users out quite a lot of times.
Yes, I do that too. my DHCP range is 100-255, and my servers and printers and stuff that should never move and I want to know where they are live <100 and are static. I have specific ranges for specific machines like pure file servers or network essential boxes (pihole) are <10. Servers for other services (Roon, time machine, torrents etc) are 10 - 50. And printers and other appliances live 50 - 100.
The other transient crap like phones tablets laptops etc that connect via Wi-Fi live in the bad side of town >100. They can fight it out with my 9 nest smoke detectors, doorbell, thermostats etc. I should put the IoT stuff on it’s own VLan but I haven’t bothered. It’s more fun to putter in the shop.