Document trade-offs in string store-type mappings

For example, is it a good idea, in terms of performance concerns, to use the default convention and let all string properties be mapped to nvarchar(max) columns, or it's better to set a fixed length (e.g. 500) globally to all string properties?

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#### Document Details

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* ID: 8d6f6f7b-b8d3-df80-33b7-46b0b98acd29
* Version Independent ID: 1a74a6d8-0ad4-9a22-d62e-1a2bab8b80b1
* Content: [Maximum Length - EF Core](https://docs.microsoft.com/en-us/ef/core/modeling/max-length)
* Content Source: [entity-framework/core/modeling/max-length.md](https://github.com/aspnet/EntityFramework.Docs/blob/master/entity-framework/core/modeling/max-length.md)
* Product: **entity-framework**
* GitHub Login: @rowanmiller
* Microsoft Alias: **divega**