In general, the email ending you choose will mostly be determined by your relationship with the recipient. When in doubt, it’s best to play it safe in professional contexts and use a neutral sign off. Keep in mind that even in digital communication you’re representing not only yourself but also your company. Your email sign off should reflect this. Try to match the tone and word choice of the person you’re corresponding with - are they already signing off with their first name or are they keeping things formal?
You can get a sense of how casual you can be based on certain characteristics of the email recipient - for example, their position, age, and company culture/culture in their sector. In the startup scene, communication is usually very casual from the start. When it comes to banks, insurance, and government offices, communication will probably stay on the level of more formal email etiquette.