aurora mysql - migrating large tables

We have write intensive application using aurora mysql 3.02 with 2xlarge instance size in prod. I want to migrate 10 tables (biggest one being 450GB) from 2nd aurora mysql into this prod db. Tried using DMS, which affects the write process due to db load. On average this db have 2500-4000 iops. Question is, if i change the instance class to bigger size, say 8xlarge. will it help, DMS & write process to get through without any issues. If the 8xlarge helps resolve the issue, would it be recommended to run DMS with indexes on the target table OR create indexes after data is migrated? Is there any suggestions, do's & dont's on this scenario from your experience? please advise