If I understand you correctly then the below amendment should do it:

Function Equilibrium(rng As Range, z As Integer)
Dim buyVar As Variant, priceVar As Variant, sellVar As Variant
Dim kumBuyVar As Variant, kumSellVar As Variant, minVar As Variant
Dim x As Long, rtb As Double, rts As Double
Dim mPrice() As Double, mMin() As Double, naqVar() As Double, y As Long
buyVar = Application.Index(rng, , 1)
priceVar = Application.Index(rng, , 2)
sellVar = Application.Index(rng, , 3)
ReDim kumBuyVar(1 To UBound(buyVar))
For x = 1 To UBound(buyVar)
rtb = rtb + buyVar(x, 1)
kumBuyVar(x) = rtb
Next x
ReDim kumSellVar(1 To UBound(buyVar))
For x = UBound(buyVar) To 1 Step -1
rts = rts + sellVar(x, 1)
kumSellVar(x) = rts
Next x
ReDim minVar(1 To UBound(buyVar))
For x = 1 To UBound(buyVar)
minVar(x) = Application.Min(kumBuyVar(x), kumSellVar(x))
Next x
For x = 1 To UBound(buyVar)
If minVar(x) = Application.Max(minVar) Then
ReDim Preserve mPrice(y): mPrice(y) = priceVar(x, 1)
ReDim Preserve mMin(y): mMin(y) = minVar(x)
ReDim Preserve naqVar(y): naqVar(y) = Application.Max(kumBuyVar(x), kumSellVar(x)) - mMin(y)
y = y + 1
End If
Next x
For x = 0 To UBound(mPrice)
If naqVar(x) = Application.Min(naqVar) Then
If z = 1 Then
Equilibrium = mPrice(x)
ElseIf z = 2 Then
Equilibrium = mMin(x)
End If
Exit Function
End If
Next x
End Function

This could also be done with a formula if using Excel 365:

=LET(rng,B2:D21,
kb,SCAN(0,INDEX(rng,,1),LAMBDA(a,b,a+b)),
kst,SORT(HSTACK(ROW(rng),INDEX(rng,,3)),1,-1),
ks,SORTBY(SCAN(0,INDEX(kst,,2),LAMBDA(a,b,a+b)),INDEX(kst,,1),1),
aq,BYROW(kb&","&ks,LAMBDA(x,MIN(--TEXTBEFORE(x,","),--TEXTAFTER(x,",")))),
naq,BYROW(kb&","&ks,LAMBDA(x,MAX(--TEXTBEFORE(x,","),--TEXTAFTER(x,",")))),
tbl,HSTACK(rng,aq,naq-aq),
ftbl,FILTER(tbl,(INDEX(tbl,,4)=MAX(INDEX(tbl,,4)))*(INDEX(tbl,,5)=MIN(INDEX(tbl,,5)))),
TRANSPOSE(CHOOSECOLS(ftbl,2,4)))

File attached with both formula and updated code.