Topic: Different ACNH data between 2 switches & 2 accounts

I have a few specific questions I can't seem to find the answer to anywhere. I've seen droves of people asking about 2 switches,1 digital, and 1 physical copy of animal crossing and not being able to play together because they get a pop up saying they share downloadable content. I have 2 switches and 2 accounts on both switches, I also have 2 physical copies of Animal Crossing. Can I have cloud data enabled and have an island on each switch with opposite profiles being the main account for their respective switches animal crossing island and the other be an additional resident on the same switch and it not mess up eachothers island saves or not let us travel to eachothers islands from our own switches. Do I need to move my whole profile to one switch and keep the other profile off of it to keep data from getting messed up or can they coexist?
I've got Mario Kart and Mario Party progress that I'd like to keep on the 1st switch because I'll probably only play it with friends on that switch and would like to have that progress on there vs having to make a different unlinked account and start over if it's possible to avoid it.

@ToBeanOrNotToBean I'm having a hard time following your question, but the Switch system only allows one ACNH island per console. If you have a secondary switch with the same nintendo account linked to it, I think you'll be restricted to same island.

Save data is stored exclusively on the switch internal memory. Each Switch user profile is a save data profile. The console doesn't care if you have a physical game or digital game, or both, or if you alternate. When you select the switch user profile opening the game, that's the save profile you'll open with.

@WoomyNNYes I have two switches and two physical copies of the game. If I use different accounts on different switches I know they can make different islands, I want to know if an account that is primary owner of one island on one switch can be a secondary users on a different switch that someone else is the primary owner of that island or if it will overwrite/mess up one of the saves to use the same two accounts for different islands on different consoles and also try to play together on the same island or by local/online play depending on if we're playing together on one switch or our separate switches. Is it possible to do this with two accounts or do I have to make 4 accounts so it doesn't mess up the data?

@ToBeanOrNotToBean Only allowing one ACNH island on a console is a very hard set rule. It's been a sticking point since the game's launch. If you think that's disappointing, many would agree.

Edit: Short answer, no. If Nintendo account 1 has it's own island on Switch 1, then it cannot be a secondary player on Switch 2/ACNH island 2. /Edit

So you have Switch 1 with Nintendo account 1, which has it's own island, ACNH island 1. If you want Switch 2 to have it's own island, then I believe Switch 2 can only have Nintendo account 2 on it when you start your ACNH game on there. Afterwards, if you link Nintendo account 1 to Switch 2, there will be an ACNH island conflict. I don't know how the conflict will be expressed. Be ready to get blocked by the system in some way. Either Switch 2 will not allow you to play ACNH with Nintendo account 1/ACNH island 1. Or maybe Switch 2 will block adding Nintendo account 1 altogether just because it already has it's own island already on Switch 1.

@ToBeanOrNotToBean If you want to play as a secondary player on one of your islands, you'd have to start from scratch & create a new Switch user (and I think another nintendo account?).