As an AWS admin in your organisation, you should try to keep the number of distinct instance families to a minimum count. In an account with 500 instances, it is better to limit the number of distinct EC2 instance families to 10 or 15. Having 50 different instance families will make it very very difficult to buy EC2 instance savings plan.
EC2 instance savings plan offer more discounts as compared to compute savings plan. If you can keep your instances confined to a set of instance families, you can easily buy EC2 instance savings plan instead of the more flexible compute savings plan. To give you an idea, on an m6g.large instance, compute savings plan will give you a 26% discount over the on demand price but EC2 instance savings plan will give you roughly 38% discount on the same. In this article, all things are applicable only to EC2 instance savings plan.
EC2 instance savings plan are not tied to a particular instance. They are tied to an instance family and region. As long as you have enough instances of the family running, you will continue to get discounts. This is the reason you should try to standardise instances in your account. Doing this can make it very easy to go with this plan instead of the compute savings plan.