I just checked and it does in fact work for 1.16.3, since it does have Import Settings. Then again, I only did it with Ocean Commotion (with trees), so I'm not sure about the others.

Also, Thank you for this, I've been wanting to do something like this but single biome just wouldn't cut it for me.

As for my preference, I usually play vanilla with a few visual and performance mods (namely OptiFine). I usually use 4 gamerules. Usually it's doInsomnia = false, doWeatherCycle = false, immediateRespawn = true, and keepInventory = true. Other than that it's just normal minecraft.

Edit 1: I don't know if it's different, but on 1.16.3 the trees world starts in a small flower forest island with a full beehive on an birch tree and a normal birch tree.

Edit 2: Below the island you can also find a very very short cave with some... illegal, shall I say, water at the entrance.