How difference are phrases

Hi there,
This is my first time post.
I want to know the difference in nuance.
Which phrases are preferable?

  1. Stay safe and healthy.
    2.Please stay safe and healthy.
    3.Kindly stay safe and healthy.
    I will send the one of them to a high position person as a business partner in the conventional company.
    Thank you for your advice!

Here is my opinion. And it is my opinion with which others may disagree.
#1 is common, and may be more common on a conversational level.
#2 might be what you want to use with your highly placed business partner.
#3 sound slightly unusual. I would not use “kindly” in this situation, but it is grammatical and has the proper meaning.

Edit: “Kindly” can be used to slightly soften a demand in a formal way. A letter from a company to someone who is late making a payment might say, “Kindly attend to this matter as soon as possible.” That is not the usage that you want.

Thank you for your advice. I understand those nuances. I will use them for a reference.