You can use any values up to 15. The main thing is not to use the cheat in the Administrator's Challenge. I also advise not to rise above 50th place in the PvP rating. The developers periodically check the results of these two game modes.
Aight bet thank you!` Main reason I asked is cause i made an initial account using max values and got banned within an hour, but thats most likely cause i didnt upgrade any of my units and i was like floor 100 on tower with like 2 units lol