Assist with creating a formula to select a table to perform a Vlookup based on two conditions.

MarindaS 

If I understand the objective clearly, I think this will do it:

=LET(
    area, XMATCH(B16, GeyserType),
    r, MAX(N(C16 = MasterKeys!$O$2:$R$5) * {1; 2; 3; 4}),
    limit, IFERROR(INDEX((Table2, Table24, Table4, Table5), r, 2, area), ""),
    IF(COUNTBLANK(B16:C16) >= 1, "", limit)
)

You may want to re-name your tables to give them descriptive names and then this formula reads even better.