How much the parameters matter probably depends somewhat on what you keep. I rarely test my nano with zoas and LPS.
My 72x24 parameters
pH 8.1-8.35 depending on time of day....Apex
salinity 1.026
temp 79.4 to 79.9...Apex
Alkalinity 8.5 with slight variations....Hanna
Calcium 440......Salifert
Magnesium 1410......Salifert
PO4 0.06 to 0.1 most of the time but can get up to 0.13 occasionally.....Hanna ULR
Nitrate 5-10......Salifert or NYOS
My 72x24 parameters
pH 8.1-8.35 depending on time of day....Apex
salinity 1.026
temp 79.4 to 79.9...Apex
Alkalinity 8.5 with slight variations....Hanna
Calcium 440......Salifert
Magnesium 1410......Salifert
PO4 0.06 to 0.1 most of the time but can get up to 0.13 occasionally.....Hanna ULR
Nitrate 5-10......Salifert or NYOS