Should you use tooltips?
Tooltips are best when they provide additional explanation for a form field unfamiliar to some users or reasoning for what may seem like an unusual request. Remember that tooltips disappear, so instructions or other directly actionable information, like field requirements, shouldn't be in a tooltip.
What can I use instead of tooltips?
You can use modals, hotspots, and in-app messages to replace tooltips.
Should buttons have tooltips?
If you're introducing the button as a new element & needs to draw users' attention you should use tooltip. It will help users to learn. *If the button explains itself clearly, we should not use tooltip.