Important Notes on Malt Substitution
Brand Variations: Even within the same "type," malts from different regions or brands will have subtle flavor differences. For example, Viking's standard Pale Malt is closer to a British profile than a neutral US 2-Row. These differences will vary in impact based on other recipe choices, they will be more apparent in a lager than they will in a double IPA or imperial stout.
Color & Modification: European malts (like Viking and Weyermann) are often highly modified and can be slightly darker than domestic US 2-Row. This generally does not require recipe adjustments for most homebrewers.
Diastatic Power: All base malts listed above have enough enzymatic power to convert their own starches and usually extra for specialty grains.
Recipe Adjustments: If substituting a very neutral malt (like US 2-Row) with a characterful one (like Maris Otter), the final beer flavor will change, which may or may not be desirable depending on the style.