Using dynamic delay you could implement using a single property
Without it, one possible way would be
property trigger_check0;
$rose(a) ##0 ( CLK_CYC == 0 ) |-> ##20 $rose(b) ##1 $fell(b);
endproperty : trigger_check0
property trigger_check1;
$rose(a) ##0 ( CLK_CYC == 1 ) |-> ##50 $rose(b) ##1 $fell(b);
endproperty : trigger_check1
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