i have my puffs farm in front of a cleared out infested mine directly at the ocean shoreline where there was a marble stair leading up to the mine.... before i found it. now the mine is just a hole in the mountain side and my small farm is right where the stair once was. could cultivate most of the small area there without needing to raise ground. and its sealed off from the rest of the biome by the water to 3 sides and 1 with the mine entrance. never made any kind of wall or defense.
only a portal and a bench to prevent spawns on the farm.
once was attacked by a 1 star seeker when i was harvesting the 50 puffs. it came flying in from the mainland but i saw it comeing a mile away already. and since seekers are idiots when flying in it tryed to lunge at me at the edge and fell down into the water and then got arrows to the knee eerrr wings since it couldnt get up again apparently.

aside that never saw enemies there. heard a blimp once but never saw it.
since puffs and caps are so efficient you really only need a farm with space for like 50 of em. as then you get 150 back plant 50 back down right away and get 100 each harvest in an infinite cycle. 100 is more than enough to cover all food needs the next harvest is ready long these run out.
if you need more just make a 2nd portal small farm.

havent found an island i could cultivate as of yet sadly. a small patch off shore with mistlands biome would be perfect but these are all that black rock ground so far :/ cannot grow anything there.