Typologically-close languages such as French and Spanish share many typological universals and macroparametric options but display different microparametric options as well as obvious and subtle morphological, syntactic and processing differences. This counterposed situation that we conceptualize as typological similarity versus typological proximity constitutes our first tool to investigate the specific characteristics of the Spanish interlanguage of L1 French (L2Sp-L1Fr) speakers. The other tool is the Competing Grammars Hypothesis (CGH) which we use as a framework to determine the optionality that results from the simultaneous availability of target-like, transferred and idiosyncratic L2Sp-L1Fr parametric options or feature combinations in the L2Sp-L1Fr interlanguage. Keywords: L1French-Spanish interlanguage; typological proximity; typological similarity; formal universals; implicational hierarchies; macroparameters; microparameters