Constexpr if alternative

You can do it the old fashioned, tried and tested tag dispatch way:

template<typename T>
void MyFuncImpl(std::true_type) {
  FunctionA<T>();
}

template<typename T>
void MyFuncImpl(std::false_type) {
  FunctionB<T>();
}

template<typename T>
void MyFunc()
{
  MyFuncImpl<T>(std::integral_constant<bool, MeetsConditions<T>::value>{});
}

One of pre-C++17 ways is to use partial template specializations, like here:

template <typename T, bool AorB>
struct dummy;

template <typename T, true>
struct dummy {
    static void MyFunc() {  FunctionA<T>(); }
}

template <typename T, false>
struct dummy {
    static void MyFunc() {  FunctionB<T>(); }
}

template <typename T>
void Facade() {
    dummy<T, MeetsConditions<T>::value>::MyFunc();
}

If you need more, than 2 specializations - you can use enum or integral value, and make specializations for all needed enums.

Another way is to use std::enable_if:

template <typename T>
std::enable_if<MeetsConditions<T>::value, void>::type
MyFunc() {
   FunctionA<T>();
}

template <typename T>
std::enable_if<!MeetsConditions<T>::value, void>::type
MyFunc() {
   FunctionB<T>();
}