You won’t hurt the tree making it into a trunk tree. Even after trimming grass will not grow well under a pine.
First rule of tree trimming is you can always take off more but it is quite hard to put back what you have removed.
Cut each limb twice. They are quite heavy and when sawing thru they will at some point break and the bark on the underside will peal. That can injure the tree. Make a shallow cut from the bottom up about a foot from the trunk then cut the limb off from the top right above the first cut. Then make a second cut closer to the trunk after the weight is gone about half inch is what I do.
As to how high to go that is up to what you want to see. I like them high enough to be able to walk under unless I want the tree for privacy to block the view.