So we are looking at doing a multisite clustering with replication across two sites. 1 site will have 320 gig log ingestion and the other will have 100 gig log ingestion. Do both sites need to have the same amount of indexers? What about storage? The size storage need to be the same as well?
You need to plan your architecture as per your requirements.
Points to consider:
1. Replication factor and Search factor, your indexer sizing will differ accordingly.
2. Replication to be only across site or within site as well.
3. Data indexing will be load balanced across cluster irrespective of site or in the particular site.