Need confirmation related to RI and SP application.

You should refer to the AWS Documentation as authoritative here, while the 3rd party may be accurate at the time that they are published, you do not know if they have been updated regularly. Always cross-check what you read in a 3rd party summary of AWS products and services and pricing, with AWS documentation.

• For savings plans refer too: https://docs.aws.amazon.com/savingsplans/latest/userguide/
• For EC2 Reserved Instances refer too: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-reserved-instances.html
• For OpenSearch Reserved Instances refer too: https://docs.aws.amazon.com/opensearch-service/latest/developerguide/ri.html
• For RedShift Reserved Nodes refer too: https://docs.aws.amazon.com/redshift/latest/mgmt/purchase-reserved-node-instance.html
• For Elasticache Reserved Nodes refer too: https://docs.aws.amazon.com/AmazonElastiCache/latest/mem-ug/CacheNodes.Reserved.html

I reviewed the diagrams mentioned in the question, and to be fair, on a high-level they are quite good. If you are trying to make a decision whether to go with Reserved Instances or Savings Plans, and trying to build a strategy for managing those commitments depending on the time & effort you are willing to invest versus the savings you'd achieve.

RIs and SPs topic, if you consider all the elements to take into consideration, are quite complex. So, I'll say that those diagrams provide a very good starting point to help you make a decision.

Maybe, I would rephrase a couple of things. For example, many images specify that certain types of RIs/SPs attributes will provide either High or Low discount. You can't always say that you'll get either high or low discount, without more context. It will often depend on combination of factors. Of course, if you decide to buy All Upfront, EC2 Instance Savings Plan, for 3yr term, you will get much higher discount and savings, compared to No Upfront, Compute SP, for 1yr term. But the difference is not always that obvious when you're comparing, for example... Partial Upfront with No Upfront in different regions and different instance families... it would be like comparing apples with oranges. And then... the fact that you'd have to calculate SP commitment yourself - that's not exactly true. If you're already running workloads for which you want to buy SP, you can get Recommendations for SP purchase in Cost Explorer (the recommendations tool is analyzing your usage and provides optimal option in terms of commitment you can make to achieve savings).