I love ordering my Niagen from Truniagen.com. Easy to understand website with many different pricing options. I chose the annual subscription for the best price. They now sell 150mg capsules, take two a day which will be 300mg a day.
Answer: Yes, its nicotinamide riboside which has been listed as safe by the FDA.
Answer: This is a rare form of Vitamin B with many benefits, so- yes.
Answer: The closest thing to TruNiagen is Elysiums BASIS and you can see the comparison here https://www.right-of-assembly.org/single-post/2018/04/14/Elysium-Basis-or-ChromaDex-Niagen----Which-Is-Best