As PP have said above, Groton is an excellent (and prestigious, since this seems to be important to you) school but as you mentioned, there are some significant differences as to fit between Groton and Andover/Exeter, particularly size.
Given that you were accepted to Groton, I recommend you celebrate! Decide with your parents whether you want to stay on the WL for Andover and Exeter, and how long you and they are willing to stay on the WL. For example, stay on it until A9? And then send the deposit to Groton and remove the other schools as options? Or are your parents willing to sacrifice the deposit at Groton, should you get off the WL? How long are you willing to deal with the uncertainty of not feeling 100% set in your plans for next year?
Did you apply to Andover and Exeter as a day student? Both of those schools require you to live in certain towns to be a day student, and there are a just few towns from which you can be a day student at both Andover and Exeter, which are pretty much 20-25 minutes from each one.
Some prospective students outside of these towns apply as a day student, telling the AO that they plan to move to one of those towns if they are accepted. Did you do this?
Day students and boarders are considered different “buckets” for admissions purposes. If you are thinking of changing your bucket, or are willing to change your bucket if it might increase your chance of getting off the WL (not sure that it will - yield for day students is usually pretty high at these schools), you or your parent definitively want to have a conversation about this with the AO ASAP.
The day student experience can also be different from the boarder experience, and that is something to seriously think about. Groton has relatively few day students compared to Andover and Exeter, so the day student experience at Groton can also be very different from the day student experience at Andover or Exeter (although I know you said you would board at Groton). These are all things your may want to really think about.